"two circles of radii 5cm and 12cm are drawn, partly overlapping. Their centres are 13cm apart. Find the area common to the 2 circles" I'm not quite sure how to do this. I think im meant to be using the area of sector as if I draw a line down the middle of the area formed I can use the 1/2r^2(x-sinx) but I don't know how I can find the angle of the triangle that is formed. Any help?