Question

If an isosceles triangle has a vertex angle of 20 degrees, then each base angle is how many degrees?

A) 20 degrees
B) 80 degrees
C) 160 degrees
D) 70 degrees

Answer 1

Step-by-step explanation:

The interior angles of ALL triangles sum to 180 degrees

20 + b + b = 180

2b = 160

b = 80 degrees

Answer 2

Each base angle of an isosceles triangle with a vertex angle of 20 degrees is 80 degrees.

Step-by-step explanation:

An isosceles triangle has two congruent sides and two congruent angles. The vertex angle is the angle between the two congruent sides. In this case, the vertex angle is 20 degrees. Since the sum of the angles in a triangle is 180 degrees, we can subtract 20 degrees from 180 to find the sum of the two base angles. Therefore, each base angle is (180 - 20) / 2 = 80 degrees.