Find the point of intersection for circle 1 & circle 2
a = ( R1 * R1 - R2 * R2 ) / ( 2 * d12 * d12 ) ; b = sqrt ( 2 * ( R1 * R1 + R2 * R2 ) / ( d12 * d12 ) - ( R1 * R1 - R2 * R2 ) * ( R1 * R1 - R2 * R2 ) / ( pow ( d12 , 4 ) ) - 1 ) / 2 ;