Hi, I need some help solving the area of a, designated in the center of this image. Below, I have two equations written out in an attempt to solve for a,but I believe I need a third linear equation in order to substitute completely. Each arc is 1/4 of a circle.

I couldn't come up with a third equation that was not a scalar multiple or combination of the other two, so I resorted to using the attached diagram and trigonometry to arrive at a solution. Diagram is attached if you're interested ...