Function to find the fourth circle 's when three radius are given
double findRadius ( double r1 , double r2 , double r3 ) { double r4 = ( r1 * r2 * r3 ) / ( r1 * r2 + r2 * r3 + r1 * r3 + 2.0 * sqrt ( r1 * r2 * r3 * ( r1 + r2 + r3 ) ) ) ; return r4 ; }