Download 6.5: Properties of Trapezoids

6.5: Properties of Trapezoids
1. Recall, what is a trapezoid? A quadrilateral that has at
Brinkman
Geometry
least one pair of parallel sides.
3. Define Trapezoid Angle Theorem: In a trapezoid, consecutive angles between a pair of
parallel sides are supplementary.
4. Apply: In the trapezoidal window at the right,
Two angles are given. Find the other two angles!
𝑚∠𝐴𝐵𝐶 𝟖𝟓
𝑚∠𝐴𝐷𝐶 𝟏𝟑𝟑
5. Isosceles Triangles are also related to ISOSCELES TRAPEZOIDS
6. Apply: The figure at the right is a water slide of a Mayan
Temple. Notice that the trapezoid formed at the base is from an
isosceles triangle. Draw the perpendicular bisector of the large
isosceles triangle.
This line is also the reflection – symmetric line.
7. Define Isosceles Trapezoid Symmetry Theorem: The perpendicular bisector of the base of an
isosceles trapezoid is also the perpendicular bisector of the other base. Therefore this is a
reflection-symmetric line for the trapezoid.
8. Mark the congruencies of the isosceles trapezoid
at the right. Label line of symmetry, perpendicular
bisector, and congruent angles.
9. Define Isosceles Trapezoid Theorem: In an isosceles trapezoid, the non-base sides
are congruent. *Mark in the trapezoid above*
10. Recall, what is a rectangle? A quadrilateral with four right angles.
11. Define Rectangle Symmetry Theorem: The perpendicular bisectors of the sides of the
rectangle are symmetry lines for the rectangle.
12. Proof time!