通过圆心和半径来算2个圆的交点

-(void)point1:(CGPoint)point1 point2:(CGPoint)point2 {

    CGFloat l= [self distanceWith:point1 point2:point2];
    CGFloat k1= (point2.y - point1.y)/(point2.x-point1.x);
    CGFloat k2 = -1/k1;

    CGFloat CE = sqrtf(50*50 + l/2*l/2);
    CGFloat AE = CE;

    CGFloat x0 = point1.x + (point2.x -point1.x)*AE/l;

    CGFloat y0 = point1.y + k1*(x0-point1.x);


    CGFloat EF = sqrt(CE/(1+k2*k2));
    CGFloat x1 = x0 - EF;

    CGFloat y1= y0+EF;

   CGFloat  cos =(((50*50) + (l/2*l/2)- AE*AE) / 2*50*l/2);
 ;
    CGFloat rads = (sinf(((50*50) + (l/2*l/2)- AE*AE) / 2*50*l/2));
    NSLog(@"=====____----++++%f", cos*180/M_PI);

    NSLog(@"=======%f %f  %f  %f %f ",x0,y0 ,x1 ,y1,rads);

}