Then, according to ∠ 1+∠2+∠3= 180 degrees, we can get:

∠1+2 * ∠1+3 * ∠1= 6 * ∠1=180 degrees, then ∠/kloc-0.

∠2=60 degrees, ∠3=90 degrees.

So, this is a right triangle.