Page 34 - Math Course 3 (Book 2)

Properties of Trapezoids
Mo. 7

Lesson 6 THEOREM 7.20

The median of a trapezoid is parallel to the bases,
and its measure is one-half the sum the measures
KEY CONCEPTS: of the bases.
1
1. Recognize and apply the properties of Example: EF = (AB + DC)
trapezoids. 2
2. Solve problems involving the medians of A A
trapezoids.
3. Recognize and apply the properties of E F
isosceles trapezoids.
D C

MO. 7 - L6a

Recognizing the Properties of Let’s Begin
Trapezoids

Vocabulary A-Z Proof of Theorem 7.19

Let us learn some vocabulary Example

trapezoid
a quadrilateral with exactly one pair of opposite Write a flow proof.
parallel sides called bases. Given: KLMN is an isosceles trapezoid.

base Prove: ∠LKM ≅ ∠MNL
A B
leg leg L M
D C
base

∠A and ∠B are base angles
∠C and ∠A are base angles. K N

Proof:

median KLMN is an isosceles trapezoid.
The segment that joins the midpoints of the legs Given
of a trapezoid is called the median.

KM ≅ NL KL ≅ MN LM ≅ ML
Def. of isos. Def. of isos. Reflexive Prop.

Median trap. are ≅. trap.

△KLM ≅ △NML
SSS

∠KLM ≅ ∠NML
CPCTC

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