Post on 29-Dec-2015
8.5 Trapezoids
Trapezoids
You will learn to identify and use the properties of trapezoidsand isosceles trapezoids.
1) Trapezoid
Trapezoids
A trapezoid is a ____________ with exactly one pair of ____________.quadrilateral parallel sides
T
P A
R
The parallel sides are called ______.bases
base
baseThe non parallel sides are called _____.legs
leg leg
Each trapezoid has two pair ofbase angles.
base anglesT and R are one pairof base angles.
P and A are the other pair of base angles.
Trapezoids
Theorem8-13
The median of a trapezoid is parallel to the _____, basesand the length of the median equals _______________ of the lengths of the bases.
one-half the sum
C
N
B
D
M
A
MNDCMNAB || ,||
DCABMN 2
1
Trapezoids
C
N
D
M
BA
Find the length of median MN in trapezoid ABCD if AB = 16 and DC = 20
16
20
DCABMN 2
1
20162
1MN
362
1MN
18MN
18
Trapezoids
If the legs of a trapezoid are congruent, the trapezoid is an _________________.isosceles trapezoid
In lesson 6 – 4, you learned that the base angles of an isosceles triangle arecongruent.
There is a similar property of isosceles trapezoids.
Trapezoids
Theorem8-14
Each pair of __________ in an isosceles trapezoid is congruent.base angles
Z Y
XW
XW
YZ
Trapezoids
T
P A
R
60°
Find the missing angle measures in isosceles trapezoid TRAP.
P A
mP = mA
60 = mA
60°
Theorem 8 – 14
T R
P + A + 2(T) = 360
Theorem 8 – 14
60 + 60 + 2(T) = 360
120 + 2(T) = 360
2(T) = 240
T = 120
120°
R = 120
120°
Trapezoids