2. 1.-DEFINITION AND PARTS
◦ An angle measures the amount of turn.
◦ Parts of an Angle
The corner point of an angle is called the vertex
And the two straight sides are called arms
The angle is the amount of turn between each
arm.
ANGLES
3. 2.-LABELLING ANGLES
◦ There are two main ways to label angles:
1. by giving the angle a
name, usually a lower-case
letter like a or b, or
sometimes a Greek letter
like α (alpha) or θ (theta)
2. or by the three letters
on the shape that define the
angle, with the middle letter
being where the angle
actually is (its vertex).
Example angle "a" is "BAC",
and angle "θ" is "BCD"
ANGLES
4. 3.- NAMES OF ANGLES
3.1. ACUTE ANGLES
◦ An Acute Angle is less than 90°
ANGLES
5. 3.- NAMES OF ANGLES
3.2. RIGHT ANGLES
◦ A right angle is an internal angle which is equal
to 90°
ANGLES
6. 3.- NAMES OF ANGLES
3.3. OBTUSE ANGLES
◦ An Obtuse Angle is more than 90° but less
than 180°
ANGLES
7. 3.- NAMES OF ANGLES
3.4. STRAIGHT ANGLES
◦ A straight angle is 180 degrees
ANGLES
8. 3.- NAMES OF ANGLES
3.5. REFLEX ANGLES
◦ A Reflex Angle is more than 180° but less
than 360°
ANGLES
10. 4.- SUPPLEMENTARY ANGLES
◦ Two Angles are Supplementary if they add up
to 180 degrees.
These two angles (140° and
40°) are Supplementary
Angles, because they add up to
180°.
Notice that together they make
a straight angle.
But the angles don't have to be
together.
These two are supplementary
because 60° + 120° = 180°
http://www.mathsisfun.com/geometry/supplementary-angles.html
ANGLES
11. 5.- COMPLEMENTARY ANGLES
◦ Two Angles are Complementary if they add up
to 90 degrees (a Right Angle).
These two angles (40° and
50°) areComplementary
Angles, because they add up
to 90°.
Notice that together they make
a right angle.
But the angles don't have to be
together.
These two are complementary
because 27° + 63° = 90°
http://www.mathsisfun.com/geometry/supplementary-angles.html
ANGLES
12. ◦ 1.-TRANSPORTING
◦ We transport angles with compass
◦ To transport angles with compass, we carry
two key measures of the angle:
- The radius of the arc
- The chord of the arc
http://recursostic.educacion.es/artes/plastic/web/cms/index.php
?id=179
WORKING WITH ANGLES
13. ◦ 2.-ADDITION
◦ We transport the two angles with compass as
before.
4
2
A
1
B
4
3
A B
3
2
1
WORKING WITH ANGLES
14. ◦ 2.-SUBTRACTION
◦ We transport the two angles with compass as
before.
4
2
A
1
B
3
4
2
A
B
3 1
WORKING WITH ANGLES
15. Bisector angle is the line segment that divides
the angle into two equal parts.
http://recursostic.educacion.es/artes/plastic/web/cms/index.ph
p?id=190
BISECTOR ANGLES
