Question

The measure of the vertex angle of an

isosceles triangle is 66°. What is the
measure of each of the base angles?

Answer 1

Since an isosceles triangle has two congruent angles (the base angles), let x be the measure of each base angle. Then we know that the sum of the three angles in a triangle is 180 degrees, so:

vertex angle + base angle + base angle = 180

66 + x + x = 180

2x + 66 = 180

2x = 114

x = 57

Therefore, each base angle measures 57 degrees.