# Thread: Find value of angle alpha

1. ## Find value of angle alpha

Been stuck for a while any hints? D:

AB=BC=ED

2. ## Re: Find value of angle alpha

Hi,
The answer is $\alpha=125$. Crucial to the proof is the fact that triangle AEB is isosceles. I tried unsuccessfully to prove this using geometry only. However, there is a simple proof using trigonometry. The first attachment separates this fact as a lemma and the second attachment solves your problem.