Name: 
 

Isosceles Triangle Theorem



 1 

The accompanying diagram shows the roof of a house that is in the shape of an isosceles triangle.  The vertex angle formed at the peak of the roof is 84°.

mc001-1.jpg

What is the measure of x?
a)
138°
c)
84°
b)
96°
d)
48°
 

 2 

Tina wants to sew a piece of fabric into a scarf in the shape of an isosceles triangle, as shown in the accompanying diagram.

mc002-1.jpg

What are the values of x and y?
a)
mc002-3.jpg
c)
mc002-5.jpg
b)
mc002-4.jpg
d)
mc002-6.jpg
 

 3 

In isosceles triangle DOG, the measure of the vertex angle is three times the measure of one of the base angles.  Which statement about mc003-1.jpg is true?
a)
mc003-5.jpg is a scalene triangle.
c)
mc003-7.jpg is a right triangle.
b)
mc003-6.jpg is an acute triangle.
d)
mc003-8.jpg is a obtuse triangle.
 



 
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