My class is 'learning' about proofs and whatnot, but I can't wrap my head around the problem my teacher assigned us for homework.

Given: Rhombus ABCD

Prove: ACE is isosceles

I know it's isosceles. I mean, it's just one of those things you look at and know. I can't say that, though, and I have no clue where to start or how to go about proving something that seems so obvious to me.

EDIT: Yo entiendo. 8D