2010 · Q52
ABC is a triangle. The internal bisector of ∠ABC and the external bisector of ∠ACB meet at D. Which one of the following is correct ?
Elementary MathematicsGeometry
- A∠BDC = ∠BAC
- B∠BDC=1/2 ∠BAC
- C∠BDC = ∠DBC
- D∠BDC = 1/2 ∠ABC
Explanation
∠BDC=½∠BAC (excentre theorem).