In the diagram below, the two circles have equal radii. However after much bashing around with angles, I was not able to show that $AX=AY$.
My only idea so far is to try to instead prove that $\angle AXY = \angle AYX$, yet I was still unable to do this. We of course need to incorporate the fact that both circles have equal radii at some point, but I cannot see a way of doing this without lots of constructions and tedious angle chasing.


The small arcs $AX$ of the left circle and $AY$ of the right circle both span the same angle $\angle ABY$.