8.3   quadrilaterals
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8.3 quadrilaterals

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8.3 quadrilaterals Presentation Transcript

  • 1. Lesson 8.3 , For use with pages 416-419 Classify the triangle by its side lengths. 1. 2.
  • 2. Lesson 8.3 , For use with pages 416-419 Classify the triangle by its side lengths. ANSWER isosceles 1. ANSWER equilateral 2.
  • 3. Quadrilaterals Section 8-3 P. 416-419
  • 4. Essential Questions
    • Why is it important to be able to identify congruent triangles in everyday life?
    • Where in real life can you use the properties of isosceles and equilateral triangles?
    • How are the relationships between lines and planes used in the real world?
    • What areas in the real world are properties of parallel lines important?
  • 5. Quadrilaterals
    • Quadrilaterals are named for the number of sides. Quad means four, so a quadrilateral is 4-sided figures.
    • Some quadrilaterals are very perfect – like a square, and others are very generic.
  • 6.
    • Quadrilateral = a closed figure made with four sides that are line segments.
      • The sum of the four angles in any quadrilateral equals 360 degrees.
    • Trapezoid = a quad. with exactly ONE PAIR of parallel sides.
    • Parallelogram = two pairs of parallel sides
    • Rhombus = parallelogram with 4  sides
    • Rectangle = quad. with 4 right angles
    • Square = a rectangle with 4  sides
  • 7. Quadrilaterals Parallelograms Rectangle Square Rhombus Trapezoid
  • 8. Diagonal
    • A diagonal of a polygon connects two vertices that do not share a side.
    • Trapezoid ABCD, name the diagonals
    A B C D Diagonal AC
  • 9. The quadrilateral is a parallelogram with 4 sides of equal length. So, it is a rhombus. EXAMPLE 1 Classifying a Quadrilateral Classify the quadrilateral. The quadrilateral is a parallelogram with 4 sides of equal length and 4 right angles. So, it is a square. a. b.
  • 10. Quadrilaterals
    • As with triangles, all quadrilaterals have a common characteristic. The sum of the 4 angles in a quadrilateral always equals exactly 360 degrees.
    90 x 4 = 360 2 @ 45 = 90 2 @ 135 = 270 Total sum of 360
  • 11. EXAMPLE 2 Finding an Unknown Angle Measure SOLUTION The sum of the angle measures is 360 . Add. Subtract 309 from each side. Find the value of x . x + 51 + 129 + 129 = 360 x + 309 = 360 = x 51
  • 12. GUIDED PRACTICE for Examples 1 and 2 ANSWER x = 65 Use the figure at the right. 1. Classify the quadrilateral. ANSWER The quadrilateral is a trapezoid with exactly 1 pair of parallel sides. 2. Find the value of x .
  • 13. Classzone.com
    • Go to the 8 th grade math book
    • Animations
    • Click on the left side on Chapters 7-9
      • Chapter 8: Drawing Quadrilaterals
        • Chapter 8: Playing Golf with Angles
  • 14. Homework
    • Assignment: p. 417 – 418 #1-14, 19-24
    • When classifying, be as specific as possible and you only need to use one name.
    • #6-8 You do NOT need to measure the quadrilaterals.