A ball rolls into a corner of a room, where it touches both walls (and, obviously, the floor). A

Question

A ball rolls into a corner of a room, where it touches both walls (and, obviously, the floor). A
larger ball rolls into the same corner so that it touches both walls and the first, smaller ball.
The small ball has a radius 1 inch. What is the radius of the large ball?

I don't want the answer, I just want to know how to find the answer.