Question

In an isosceles triangle, the base angles are equal. The vertex angle is 40°. What are the base angles of the triangle? (Remember, the sum of three angles of a triangle is 180°).

Answer 1

Let the base angles be equal to b.

The sum of all interior angles of a triangle is 180°.

b + b + 40° = 180°

2b + 40° = 180°

2b = 180° - 40°

b = 140°      ...(Transposing 40° to R.H.S.)

Dividing both sides by 2,

`(2b)/2 = (140°)/2`

b = 70°

Therefore, the base angles of the triangle are of 70°.