An isosceles triangle is a triangle in which two sides are equal in length. The angle between the two equal sides is called the vertex angle, while the other two angles are called the base angles. If the vertex angle is 60°, what is the measure of the base angles?
A)50°
B)60°
C)45°
D)80°
E)65°

Question

Quizplus · Accepted Answer

In an isosceles triangle, the two base angles are equal, and the sum of all angles in any triangle is 180°. Given the vertex angle is 60°, the sum of the two base angles is 180° - 60° = 120°. Since the base angles are equal, each is 120° / 2 = 60°.

An Isosceles Triangle Is a Triangle in Which Two Sides