1. What is the area formula for a trapezoid?
5-2B Planning a Proof
What is a rhombus?
What is a trapezoid?
What is the area formula for a trapezoid?

2. Definitions A rhombus is a quadrilateral with four congruent sides.
(All rhombuses are parallelograms.)
A trapezoid is a quadrilateral with exactly one pair of parallel sides. The parallel sides are the bases of the trapezoid, and the nonparallel sides are its legs.
base
leg

3. Classify each quadrilateral as a square, rectangle, rhombus, parallelogram or trapezoid.
rectangle, parallelogram
trapezoid
square, rectangle, rhombus, parallelogram
trapezoid
rhombus,
parallelogram

4. Proof If a quadrilateral is a rhombus, then it is a parallelogram.
Given: Quadrilateral ABCD is a rhombus
Prove: ABCD is a parallelogram A B C D
Statements
Draw line AC
Reasons
Two pts determine line
Def of Rhombus
Reflexive
SSS
CPCTC
Alt Int angle congruent, lines ||

5. Theorem
The area of a trapezoid is the product of half the sum of the bases (b1 and b2) and the height (h).

6. Find the area of the trapezoid9
4.5
5.5
5 cm
14 cm 2 6 8
37.125
47.5 cm2 30

7. What is a rhombus?
A rhombus is a quadrilateral with four congruent sides.
What is a trapezoid?
A trapezoid is a quadrilateral with exactly one pair of parallel sides.
What is the area formula for a trapezoid?

8. Assignment 5-2B
Worksheet 5.2B