Question

求点p（x0，y0）关于Ax+By+C=0的对称点坐标。要快

Answer 1

设p(x1,y1)
当A=0时，可解出x1=x0,y1=(-2c/B)-y0;当B=0时,可解出x1=(-2c/A)-x0,y1=y0
当AB不等于0时
因为是对称点，线段中点在直线上：A(x1+x0)/2+B(y1+y0)/2+c=0
垂直：(y1-y0)/(x1-x0）*（-A/B）=-1
解出x1=-(2cA+ABy0-x0B^2y0)/(A^2+B^2y0),y1=(x1-x0)B/A+y0

Answer 2

设坐标（x，y），然后（（X0+X)/2,(Y0+Y）/2）代入方程求X,Y

Answer 3

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