1. The problem statement, all variables and given/known data ABC is a triangle. The bisector of the exterior angle at B and the bisector of ∠C intersect each other at D. Then prove that ∠D=90°-(∠A/2) 2. Relevant equations 3. The attempt at a solution I guess I want to prove an untrue thing because by drawing a diagram and working out I get ∠D=∠A/2. I think I have drawn it wrong by mis-understanding the question. Or the question is an error? Or did I work out wrong?