I want to draw 2 circles of the same size that have a specified percentage of area overlapping.

For instance, if the overlapping percentage is 0%, the circles are next to each other and the distance between the centers is equivalent to the radius. If the overlapping percentage is 100%, they are completely on top of each other (looking like 1 circle), and the distance between the centers is 0. If the overlapping percentage is 50% they intersect so that 50% of their area is overlapping.

What is an equation that gives you the distance that the center of the circles need to be from each other to satisfy a given percentage of area overlapping?