CK-12 Geometry Concepts

http://www.ck12.org Chapter 6. Polygons and Quadrilaterals

Example C

Findx. All figures are trapezoids with the midsegment.

Answers:

1. a)xis the average of 12 and 26.^12 + 226 =^382 = 19

b) 24 is the average ofxand 35.

x+ 35

2

= 24

x+ 35 = 48

x= 13

c) 20 is the average of 5x−15 and 2x−8.

5 x− 15 + 2 x− 8

2

= 20

7 x− 23 = 40

7 x= 63

x= 9

Watch this video for help with the Examples above.

MEDIA

Click image to the left for more content.

CK-12 Foundation: Chapter6TrapezoidsB

Concept Problem Revisited

Given an isosceles trapezoid withm^6 B= 38 ◦, find the missing angles.

In an isosceles trapezoid, base angles are congruent.

(^6) B∼= (^6) Cand (^6) A∼= (^6) D
m^6 B=m^6 C= 38 ◦
38 ◦+ 38 ◦+m^6 A+m^6 D= 360 ◦
m^6 A=m^6 D= 142 ◦
Vocabulary
Atrapezoidis a quadrilateral with exactly one pair of parallel sides. Anisosceles trapezoidis a trapezoid where the
non-parallel sides and base angles are congruent. Themidsegment (of a trapezoid)is a line segment that connects
the midpoints of the non-parallel sides.