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Síntesis de las matemáticas de secundaria y preparatoria

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### Math synthesis

1. 1. ASMaths Snezana Lawrence © 2007
2. 2. Snezana LAWRENCE © 2007 AS Mathematics summary notes downloaded from www.mathsisgoodforyou.comThese summary notes for the AS Mathematics (covering all exam boards for England and Wales) have been written by Dr. Snezana Lawrence made possible by funding fromGatsby Technical Education projects (GTEP) as part of a Gatsby Teacher Fellowship ad- hoc bursary awarded during the academic 2006/7. Responsibility for the materials lies with the author, and GTEP cannot accept anyliability for the content of these materials or any consequences arising from their use. All graphics have been designed by Snezana Lawrence; permission for reproduction should be made to Snezana Lawrence. www.mathsisgoodforyou.com snezana@mathsisgoodforyou.com Snezana LAWRENCE © 2007 2
3. 3. Snezana LAWRENCE © 2007 AS Mathematics summary notes downloaded from www.mathsisgoodforyou.comCONTENTSSURDS AND INDICES ...................................................................................................................................... 5 INTRODUCTION – NUMBER SETS ....................................................................................................................... 5 RATIONALISING THE D ENOMINATOR ............................................................................................................... 5 LAWS ON INDICES .............................................................................................................................................. 6 COMMON MISTAKE ............................................................................................................................................ 6ALGEBRA – DIFFERENCE OF SQUARES AND FEW OTHER THINGS ........................................... 7 ALGEBRAIC EXPRESSIONS ................................................................................................................................ 7 FUNCTIONS AND POLYNOMIALS ....................................................................................................................... 7 USEFUL PRODUCTS AND FACTORISATIONS FOR A LGEBRAIC MANIPULATION ............................................... 7 COMMON MISTAKE ............................................................................................................................................ 7BINOMIAL EXPANSION ................................................................................................................................. 8 INTRODUCTION – WHAT IS IT ALL ABOUT ......................................................................................................... 8 USING PASCAL’S TRIANGLE .............................................................................................................................. 8MORE ALGEBRA .............................................................................................................................................. 9 DIVISION OF POLYNOMIALS .............................................................................................................................. 9 REMAINDER THEOREM .................................................................................................................................... 10 FACTOR THEOREM .......................................................................................................................................... 10SOLVING QUADRATIC EQUATIONS....................................................................................................... 11 GENERALLY SPEAKING… ............................................................................................................................... 11 COMPLETING THE SQUARE .............................................................................................................................. 11SKETCHING QUADRATICS ........................................................................................................................ 13 FIRST THINGS FIRST - WHAT IS QUADRATIC? ................................................................................................. 13TRIGONOMETRIC FUNCTIONS................................................................................................................ 15 RADIANS .......................................................................................................................................................... 15 THE SPECIAL TRIANGLES ................................................................................................................................. 15 GRAPHS OF TRIGONOMETRIC FUNCTIONS ...................................................................................................... 16 TRIGONOMETRIC IDENTITIES .......................................................................................................................... 16APPLICATIONS OF TRIGONOMETRY.................................................................................................... 17 AREAS AND LENGHTS ..................................................................................................................................... 17 SINE AND COSINE RULES ................................................................................................................................. 17LOGARITHMS ................................................................................................................................................. 18 DEFINITION OF A LOGARITHM ........................................................................................................................ 18 LOG RULES ...................................................................................................................................................... 18 LOG FUNCTIONS & SOLVING EQUATIONS...................................................................................................... 18EXPONENTIAL FUNCTIONS ...................................................................................................................... 19 GRAPHS OF EXPONENTIAL FUNCTIONS ........................................................................................................... 19INEQUALITIES ................................................................................................................................................ 20 LINEAR INEQUALITIES ..................................................................................................................................... 20 QUADRATIC INEQUALITIES ............................................................................................................................. 20 3
4. 4. Snezana LAWRENCE © 2007 AS Mathematics summary notes downloaded from www.mathsisgoodforyou.comSIMULTANEOUS EQUATIONS................................................................................................................... 21 DIFFERENT CASES ........................................................................................................................................... 21 USE OF THE D ISCRIMINANT............................................................................................................................. 21COORDINATE GEOMETRY OF A STRAIGHT LINE........................................................................... 23 LINE SEGMENTS............................................................................................................................................... 23 THE G RADIENT OF A LINE ............................................................................................................................... 23 PARALLEL AND PERPENDICULAR LINES ......................................................................................................... 24 EQUATION OF A LINE ....................................................................................................................................... 24 COMMON TASKS .............................................................................................................................................. 24COORDINATE GEOMETRY OF A CIRCLE ............................................................................................ 25 CIRCLE EQUATION........................................................................................................................................... 25 EQUATION OF A CIRCLE AND COMPLETING THE SQUARE ............................................................................. 25 PROBLEMS ....................................................................................................................................................... 25DIFFERENTIATION ....................................................................................................................................... 26 RATES OF CHANGE .......................................................................................................................................... 26TRANSFORMATION OF GRAPHS AND APPLICATION OF DIFFERENTIATION ..................... 28 APPLICATION OF DIFFERENTIATION – SKETCHING OF FUNCTIONS ............................................................... 28 TRANSFORMATION OF GRAPHS ....................................................................................................................... 28INTEGRATION ................................................................................................................................................ 31 THE REVERSE OF DIFFERENTIATION ............................................................................................................... 31 n RULES FOR DIFFERENTIATING AND INTEGRATING x .................................................................................. 31 AREA UNDER A CURVE .................................................................................................................................... 31 TRAPEZIUM RULE ............................................................................................................................................ 32 RULES FOR INTEGRATION OF GENERAL FUNCTIONS ..................................................................................... 33 INTEGRALS OF SIMPLE FUNCTIONS................................................................................................................. 33SEQUENCES AND SERIES ........................................................................................................................... 34 SEQUENCES ...................................................................................................................................................... 34 FORMULA FOR A LINEAR SEQUENCE ............................................................................................................... 34 FORMULA FOR A QUADRATIC SEQUENCE........................................................................................................ 34 SERIES AND ! NOTATION .......................................................................................................................... 35 ARITHMETIC SERIES ........................................................................................................................................ 35 GEOMETRIC SERIES ......................................................................................................................................... 35 4
5. 5. Snezana LAWRENCE © 2007 AS Mathematics summary notes downloaded from www.mathsisgoodforyou.comSURDS AND INDICESINTRODUCTION – NUMBER SETSReal numbers ( ! ) are all numbers that correspond to some number on a number line(whether whole – integers, or decimal numbers, positive or negative).The set of real numbers can be separated into two subsets: rational ( ! ) and irrational (nosign for them) numbers. All rational numbers can be expressed as fractions of twointegers, whereas the irrational numbers cannot.Natural numbers are positive counting numbers (1, 2, 3, etc.). They are denoted ! .Integers are whole numbers, whether positive or negative, denoted ! (and there are twosubsets to this – positive integers, !+ , and negative, !! ).Roots that cannot be expressed as rational numbers are called SURDS. Surds areexpressions containing an irrational number – they cannot be expressed as fractions oftwo integers. Examples are 2, 11, 10 . When asked to give an exact answer, leavethe square roots in your answer (although you may have to manipulate and/or rationalisethe denominator) as you can never give an exact value of an irrational number.RATIONALISING THE DENOMINATORFor historical reasons, you need to somehow always ‘get rid’ of the surd if it is in thedenominator. There are several techniques of manipulation you can use.When multiplying or dividing with surds, this may be helpful a ! b = a!b a a = b b a ! a = a2 = aWhen you get the expression which does not only have a surd in the denominator, butsomething like this: 1 5!2you need to think how to get the surd in the numerator and have denominator without anysurds. So you may want to apply the difference of squares: ( x ! y)( x + y) = x 2 ! y2This can also be applied to the case when one, or both, of the members of the brackets aresquare roots (or surds): ( x! y )( ) x + y = x!y 5
6. 6. Snezana LAWRENCE © 2007 AS Mathematics summary notes downloaded from www.mathsisgoodforyou.comSo 1 1 5+2 5+2 = i = = = 5+2 5!2 5!2 5+2 ( 5) 5!4 2 ! 22LAWS ON INDICESTo be good with surds, you also need to know all rules for INDICES: a0 = 1 !1 !11 " a% " b% a = , and \$ =\$ a # b& # a& an ( am = an+ m an an ÷ am = = an! m am n a m = m an m " a% a ( b = ( ab ) m m m , and \$ # b&COMMON MISTAKENever, ever split the sum or difference of an expression like x + y into x + y . Youcan’t do that because you have two different numbers in an expression which is of the 1form (x + y) . And as with any other powers of expressions within the brackets you can’t 2just apply the powers to the members of the brackets, but you must imagine thesebracketed expressions multiplying each other as many times as the power says.What you CAN do is break a number or a product under a root into its factors, some ofwhich will hopefully be numbers that you will be able to take outside of the root. Forexample, 27 = 9i3 = 3 3or 8x 3 = 4i2ix 2 ix = 2x 2x 6
7. 7. Snezana LAWRENCE © 2007 AS Mathematics summary notes downloaded from www.mathsisgoodforyou.comALGEBRA – DIFFERENCE OF SQUARES AND FEW OTHER THINGSALGEBRAIC EXPRESSIONSA term consists of products of numbers and letters; for example 3a 2 + 4b is a term.The numbers multiplying the letters in an expression or equation are called coefficients;for example, a and b in the following expression ax 2 +bx are coefficients.FUNCTIONS AND POLYNOMIALSRelationship between an input value and the output value defined by mathematicalexpression is called function. Function can be written asy = x 2 , or f (x) = x 2 . In both cases, this statement says that for any value of x, the valueof y, or f(x) will be the square of the original (input) value.Linear function has a form f (x) = mx + c , and the corresponding graphical presentationof this function will be a straight line.Quadratic function has a form f (x) = ax 2 + bx + c , and the corresponding graphicalpresentation will be a parabola.Polynomial has a form an x n + an !1 x n + ... + a0 x 0 . The degree of polynomial is determinedby the greatest power of x, so in this example, polynomial would have nth-degree.USEFUL PRODUCTS AND FACTORISATIONS FOR ALGEBRAIC MANIPULATIONThese are to be memorised if you can – they can be very useful to you. (a + b)(a ! b) = a 2 ! b 2 (x + a)(x + b) = x 2 + (a + b)x + ab (a + b)2 = a 2 + 2ab + b 2 (a ! b)2 = a 2 ! 2ab + b 2 (a + b)3 = a 3 + 3a 2b + 3ab 2 + b 3 (a ! b)3 = a 3 ! 3a 2b + 3ab 2 ! b 3 a 3 + b 3 = (a + b)(a 2 ! ab + b 2 ) a 3 ! b 3 = (a ! b)(a 2 + ab + b 2 )COMMON MISTAKEDon’t ever do something like (a + b)2 = a 2 + b 2 because you have missed the point that(a + b)2 actually means (a + b)(a + b) , which will give you, as above,(a + b)2 = a 2 + 2ab + b 2 . 7
8. 8. Snezana LAWRENCE © 2007 AS Mathematics summary notes downloaded from www.mathsisgoodforyou.comBINOMIAL EXPANSIONINTRODUCTION – WHAT IS IT ALL ABOUTBinomial simply means – two terms. Binomial expansion is about expanding anexpression of two terms within a pair of brackets, which are put to a power. It is anyexpression such as this:(a + b)nUSING PASCAL’S TRIANGLEYou can use Pascal’s triangle for the binomial expansion of any degree:(a + b)0 = 1(a + b) = 1 1a + 1b(a + b) = 2 1a 2 + 2ab + 1b 2(a + b)3 = 1a 3 + 3a 2b + 3ab 2 + 1b 3(a + b)4 = 1a 4 + 4a 3b + 6a 2b 2 + 4ab 3 + 1b 4Now carefully compare how the coefficients andpowers relate to Pascal’s triangleAlternative method of finding coefficients relies on the theory of combinations.n factorial is n! = n(n ! 1)(n ! 2)(n ! 3) " .... " 3 " 2 " 1By definition 0! = 1 (say ‘n choose r’).Then the formula for binomial expansion of (a + b)n = is ! n\$ ! n\$ ! n\$ ! n\$ ! n\$ ! n\$(a + b)n = # & a n + # & a n 1b + # & a n 2b 2 + # & a n 3b 3 + ...# & a n r b r + ... + # & b n " 0% " 1% " 2% " 3% " r% " n% 8
9. 9. Snezana LAWRENCE © 2007 AS Mathematics summary notes downloaded from www.mathsisgoodforyou.comMORE ALGEBRADIVISION OF POLYNOMIALSSometimes you will have to divide one polynomial by another. For example,(x 4 ! 3x + 5) ÷ (x ! 4) . The divisor is (x ! 4) , and generally divisor is considered to beof a form (x ! a) .The polynomial (x 4 ! 3x + 5) begins with a fourth power, but then doesn’t have cube orsquare term. It is wise however to still count the missing terms in the expression, but withthe coefficients 0, like this:(x 4 + 0x 3 + 0x 2 ! 3x + 5) .Now you can write this down as in long division: x ! 4 x 4 + 0x 3 + 0x 2 ! 3x + 5 .Or if you look at the coefficients of the larger expression, like this4 | 1 0 0 -3 5Now bring down the first coefficient down4 | 1 0 0 -3 5 1multiply 4 (generally a) with this first coefficient (which was brought down) and put itunder the next coefficient4 | 1 0 0 -3 5 4 1Then 0+4=4, which you write under4 | 1 0 0 -3 5 4 1 4Repeat the process4 | 1 0 0 -3 5 4 16 64 244 1 4 16 61 249 249The result will be x 3 + 4x 2 + 16x + 61 + x!4 9
10. 10. Snezana LAWRENCE © 2007 AS Mathematics summary notes downloaded from www.mathsisgoodforyou.comREMAINDER THEOREMstates that if f (x) is divided by (x ! a) the remainder is f (a) ; if f (x) is divided by ! b\$(ax ! b) the remainder is f # & . " a%FACTOR THEOREMstates that if f (a) = 0 ! (x " a) , is a factor of f (x) ! b\$And if f # & = 0 (ax ( b) is a factor of f ( x ) . " a% 10
11. 11. Snezana LAWRENCE © 2007 AS Mathematics summary notes downloaded from www.mathsisgoodforyou.comSOLVING QUADRATIC EQUATIONSGENERALLY SPEAKING…There are three main ways to solve a quadratic equation: 1. By trying to factorise it; so that you get an equation of the sort (x ! a)(x ! b) = 0 then it is easily seen that if (x ! a)(x ! b) = 0 either x = a , or x = b 2. By using the formula for solving the quadratic equation, which relates to ax 2 + bx + c = 0 !b ± b 2 ! 4ac and the two solutions would be x1,2 = 2a 3. By completing the square, so that you get something like (x ! 3)2 ! 25 = 0 which means that you can write that as (x ! 3)2 = 25 and then you can take square root of both sides, which gives you (x ! 3) = ± 25 so, x = 3 ± 5 .COMPLETING THE SQUAREAlways look to have coefficient with x to be a=1, or manipulate your equation until youhave it like that.Let us say you have a usual quadratic of a form ax 2 + bx + c = 0 , where a = 1 b You need to use half of b, so let us introduce a value k such that k = . 2 Re-write your equation as (x + k)2 ! k 2 + c = 0Because neither k 2 nor c have x ‘attached’ to them, you can tidy the equation up and thatwill be completed square of the original equation.You can also use the completed square form to sketch the graph of a quadratic faster. Theinformation given by the completed square form isy = a(x + p)2 + q 11
12. 12. Snezana LAWRENCE © 2007 AS Mathematics summary notes downloaded from www.mathsisgoodforyou.comThe vertex of parabola will have coordinates (-p,q); its axis of symmetry will be x=-p. Itwill be ! shaped if a > 0, and ! shaped if a < 0. 12
13. 13. Snezana LAWRENCE © 2007 AS Mathematics summary notes downloaded from www.mathsisgoodforyou.comSKETCHING QUADRATICSFIRST THINGS FIRST - WHAT IS QUADRATIC?Function of a form y = ax 2 + bx + cis called quadratic – and its graph is a parabola.Let us look at a specific function,To sketch it, follow these steps: 1. First look at the coefficient next to x 2 (remember that would be a). There are two possibilities  a < 0 in which case the parabola would be side up – like a hill  a > 0 in which case the parabola is like a valley In our case, a > 0 , so it is a ‘valley’. 2. You can now look at the formula for finding the roots of the function: !b ± b 2 ! 4ac x1,2 = 2a The part under the square root is called the discriminant; there are three possibilities  b 2 ! 4ac >0, in which case the function has two roots (the parabola cuts the x-axis in two places  b 2 ! 4ac =0, in which cases there is a repeated root, the parabola only touches the x-axis 13
14. 14. Snezana LAWRENCE © 2007 AS Mathematics summary notes downloaded from www.mathsisgoodforyou.com  b 2 ! 4ac <0, in which case there are no real roots – the parabola will not cut or touch the x-axis. 3. Now complete the square for this function (equate it with 0, to find the roots at the same time). For the given function, x 2 + 6x + 3 = 0 , the completed square form would be (x + 3)2 ! 9 + 3 = 0 , or when tided up, (x + 3)2 ! 6 = 0 . The roots are x= !3 ± 6 4. The completed square form gives us various information; let us think of it as being generally of a form a(x + p)2 + q a. The axis of symmetry for the parabola will be = -p ; in our case –3 b. The vertex of this parabola will be (-p, q); in our case (-3,-6) 5. We could have found the roots by either using 2, or 3, as above. In either case, we have two distinct roots in our example, and they are !3 ± 6 . These are two points at which parabola cuts the x axis, (0, !3 + 6 ), and (0, !3 ! 6 ). 6. To find where the parabola intersects with the y-axis, substitute x = 0 In our case, that would be at y = 3. 14
15. 15. Snezana LAWRENCE © 2007 AS Mathematics summary notes downloaded from www.mathsisgoodforyou.comTRIGONOMETRIC FUNCTIONSRADIANS r ! rad = 180 0 r 180 0 1 rad r 1rad = " 57.30 ! 0 180 10 = rad !Some most common values: ! in degrees Sin ! cos ! tan ! ! in radians 0 0 0 1 0 0 1 3 1 ! 30 0 2 2 3 6 1 1 ! 45 0 1 2 2 4 3 1 ! 60 0 3 2 2 3 ! 90 0 1 0 undefined 2THE SPECIAL TRIANGLES 450 300 2 2 3 1 600 450 1 1 15
16. 16. Snezana LAWRENCE © 2007 AS Mathematics summary notes downloaded from www.mathsisgoodforyou.comGRAPHS OF TRIGONOMETRIC FUNCTIONS 6 4 2 f(x) = sinx) ( -10 -5 5 10 -2 6 -4 4 -6 2 f(x) = cosx) ( -10 -5 5 10 -2 6 -4 4 -6 2 f(x) = tanx) ( -10 -5 5 10 -2 -4TRIGONOMETRIC IDENTITIES -6For all values of ! :sin ! = tan ! sin 2 ! + cos 2 = 1 sin ! = cos(90 0 " ! ) cos! = sin(90 0 " ! )cos! 16
17. 17. Snezana LAWRENCE © 2007 AS Mathematics summary notes downloaded from www.mathsisgoodforyou.comAPPLICATIONS OF TRIGONOMETRYAREAS AND LENGHTS 1 2 B arc Area of sector, A = r! 2 Length of arc, s = r! sector c a h Area of a triangle 1 N A = ab sin C C 2 b A Area of segment, S = Area of sector – Area of triangle 1 2 1 1 S= r ! " r 2 sin ! = r 2 (! " sin ! ) 2 2 2SINE AND COSINE RULES a b cThe sine rule says that, for any triangle, = = sin A sin B sin C sin A sin B sin Cor alternatively, = = a b cThe cosine rule says that, for any triangle: a 2 = b 2 + c 2 ! 2bc cos A b2 + c2 ! a2Rearranging the cosine rule gives cos A = 2bc 17
18. 18. Snezana LAWRENCE © 2007 AS Mathematics summary notes downloaded from www.mathsisgoodforyou.comLOGARITHMSDEFINITION OF A LOGARITHMThe logarithm of a positive number to a given base is the power to which the base mustbe raised to equal the given number. ax = b For example 10 2 = 100 ! log10 100 = 2LOG RULESAs a log is a power (or index), the rules for combining logs relate to the rules combiningindices. For ANY BASE c, the rules are log c ab = log c a + log c b a log c = log c a ! log c b b log c a n = n log c a For any base a (where a > 0, a ! 1 ) a1 = a ! log a a = 1 a 0 = 1 ! log a 1 = 0 1 1 a "1 = ! log a = "1 a aLOG FUNCTIONS & SOLVING EQUATIONSLog functions and exponential functions are inverses of each other. One ‘undoes’ theother. For any base a (where a > 0, a ! 1 ) log a a x = x a loga N = N To change the BASE of the log use log c b log a b = log c aTo solve the equations involving indices and logs, of the type a x = b , you can alwaystake logs of both sides. 18
19. 19. Snezana LAWRENCE © 2007 AS Mathematics summary notes downloaded from www.mathsisgoodforyou.comEXPONENTIAL FUNCTIONSThe exponential function has the form y = a x , where , a > 0, a ! 1GRAPHS OF EXPONENTIAL FUNCTIONSAll graphs of exponential functions pass through the point (0, 1).When a>1, then the graph of exponential functions looks like this 6 4 2 f(x) = ax -10 -5 5 10 -2 -4 -6When 0<a<1, the graph looks like this 6 4 2 f(x) = ax -10 -5 5 10 -2 -4 -6 19
20. 20. Snezana LAWRENCE © 2007 AS Mathematics summary notes downloaded from www.mathsisgoodforyou.comINEQUALITIESLINEAR INEQUALITIESWhen dealing with inequalities solve them as equations, but maintain the inequality signas it originally held. It is unsafe to square both sides or take their reciprocals with theinequality in place, so be careful when doing that!If you have two or more inequalities and you are trying to find the range of values for theunknown for which they will hold, the easiest thing to do is to draw a number line andfind where the values hold in all cases. For example, find the range of values for which5<2x +1 ! 11; solving the two separately would give us5 < 2x + 1 ! 4 < 2x ! x > 2 x >22x + 1 " 11 ! 2x " 10 ! x " 5and on the number lines that would like thiswhich means that the values for which both x <=5inequalities hold are 2<x!5QUADRATIC INEQUALITIESThe easiest way is to find the roots and factorise the quadratic inequality. Look at thesigns to decide on the range of values of x required to make the inequality true.For example, solve x 2 ! x ! 6 < 0 6Factorise the corresponding equation (x ! 3)(x + 2) = 0Which means that either is x = 3 , or x = !2 . 4If we sketch the graph we would see that the range of 2values for which y<0 is enclosed by the parabola andthe x axis. Therefore the solution to the originalinequality is -10 -5 5 !2 < x < 3 -2 -4 -6 20
21. 21. Snezana LAWRENCE © 2007 AS Mathematics summary notes downloaded from www.mathsisgoodforyou.com SIMULTANEOUS EQUATIONS DIFFERENT CASES 6 Two linear equations – their single point of 4 intersection will result in one value for x and one value for y which will be the solutions to these two simultaneous 2 equations. -5 5 10 -2 -4 If you have a quadratic and linear equations there are three possible cases: 6 There will be two points of -6 There is one point of No intersections intersection, therefore 2 values intersection, 1 x and 1 y. 6 between the two lines, x and4 2 for y. therefore no common solutions. 6 4 2 4 2-5 5 10 2 -10 -5 5 10 -2 -10 -5 5 -2 -4 -2 -4 -6 -4 -6 -6 USE OF THE DISCRIMINANT Without drawing the two graphs, you can use algebraic manipulation to find the same: rearrange the linear equation and substitute it into the quadratic. A new quadratic is 21
22. 22. Snezana LAWRENCE © 2007 AS Mathematics summary notes downloaded from www.mathsisgoodforyou.comformed; use the discriminant of this new equation to see how many roots (commonsolutions) you will have for the two original equations.If d > 0 – there are two distinct rootsd = 0 – one real root (repeated root)d < 0 – no real roots. 22
23. 23. Snezana LAWRENCE © 2007 AS Mathematics summary notes downloaded from www.mathsisgoodforyou.com COORDINATE GEOMETRY OF A STRAIGHT LINE LINE SEGMENTS The length of the line segment joining two points will relate to their coordinates. Have a good look at the diagram 8 The length joining the point A and C can be found by 6 C using Pythagoras’ Theorem: 4 y2 - y1 AB 2 + BC 2 = AC 2 2 AC = AB 2 + BC 2 = (x2 ! x1 )2 + (y2 ! y1 )2 A B x2 - x1-5 5 10 Mid-point of the line can be found by using the same principle 82 - So the point between A and C will have the coordinates 64 - C y2 - y1 x1 + x2 y1 + y2 4 ( , ) 2 2 2 2 A x2 - x1 B 25 5 10 -2 -4 THE GRADIENT OF A LINE The gradient measures the steepness of the line. increase y y !y It is defined as , or m = 2 1 increase x x2 ! x1 When the gradient is 1, the line makes a 450 angle with either axes. If the gradient is 0, the line is parallel to the x axis. 23