Beside the fact that it looks like a triangle ... how can i prove this....?

what does I being the midpoint of GH tell you about HI and GI ?

I is the radius on line GH?...

In triangles EHI and FGI we have HI congruent to GI, EH congruent to FG and also we have angle EHI congruent to angle FGI. Now recall criterion for congruence of triangles. Thus you have the result.

Originally Posted by yeatch
Beside the fact that it looks like a triangle ... how can i prove this....?
You have two congruent triangles.

Why are two triangles congruent?

They have equal sides(i.e. one side of a triangle is equal to one side of another triangle) and equal angles.

What is a isosceles triangle?
They have two sides equal. What if two sides are sides of two congruent triangles?