Question

One angle of an isosceles triangle measures 40°. What measures are possible for the other two angles? Choose all that apply.

40°
100°
20°
70°

Answer 1

100° and 40°

Explanation:

In an isosceles, 2 interior angles are equal.

If one angle is 40°, another one of its angles must be also 40°.

Fact of a triangle

Sum of interior angles of a triangle is 180°.

Let the unknown angle be x.

x + 40° + 40° = 180°

x + 80° = 180°

x = (180 - 80)°

x = 100°

So, the other angle is 100°

Hence,

100° and 40° are the possible measures for the other two triangles.