# Math Help - Compute the angle A

1. ## Compute the angle A

Let ABC be a triangle with angle A < Angle C < 90° < angle B. Consider the bisectors of the external angles at A and B, each measured from the vertex to the opposite side (extended). Suppose both these line segments are equal to AB. Compute the angle A.

2. A sketch would be nice.

3. Originally Posted by perash
Let ABC be a triangle with angle A < Angle C < 90° < angle B. Consider the bisectors of the external angles at A and B, each measured from the vertex to the opposite side (extended). Suppose both these line segments are equal to AB. Compute the angle A.
The two angle bisectors intersect in point S. According to your problem triangle ABS must be an equilateral triangle which is only possible if the external angles are 120°. Therefore the internal angles must be 60°.