CK-12 Geometry-Concepts

4.10. Isosceles Triangles http://www.ck12.org

47 ◦+ 47 ◦+v= 180 ◦

v= 180 ◦− 47 ◦− 47 ◦

v= 86 ◦

Example C

If an isosceles triangle has a vertex angle with a measure of 116◦, what is the measure of each base angle?

Draw a picture and set up and equation to solve for the base angles,b. Recall that the base angles are equal.

116 ◦+b+b= 180 ◦

2 b= 64 ◦

b= 32 ◦

Watch this video for help with the Examples above.

MEDIA

Click image to the left for use the URL below.

URL: http://www.ck12.org/flx/render/embeddedobject/52627

CK-12 Foundation: Chapter4IsoscelesTrianglesB

Vocabulary

An isosceles triangle is a triangle that hasat leasttwo congruent sides. The congruent sides of the isosceles triangle
are called thelegs. The other side is called thebase. The angles between the base and the legs are calledbase angles.
The angle made by the two legs is called thevertex angle.