【数学】已知正方形相邻两点坐标求另外两点坐标

已知正方形相邻两点(a,b) or (x1, y1)与(c,d) or (x2, y2)坐标

公式：
$(x_3,y_3) = (c + (b-d), d - (a-c)) \\ (x_4,y_4) = (a + (b-d), b - (a-c)) \\ (x_5,y_5) = (a - (b-d), b + (a-c)) \\ (x_6,y_6) = (c - (b-d), d + (a-c))$
用x, y表示
$(x_3,y_3) = (x_2 + (y_1-y_2), y_2 - (x_1-x_2)) \\ (x_4,y_4) = (x_1 + (y_1-y_2), y_1 - (x_1-x_2)) \\ (x_5,y_5) = (x_1 - (y_1-y_2), y_1 + (x_1-x_2)) \\ (x_6,y_6) = (x_2 - (y_1-y_2), y_2 + (x_1-x_2))$
对称的两点横纵坐标中的第一个正负号相反，如
$(x_3,y_3)与(x_6,y_6) \\ (x_4,y_4)与(x_5,y_5)$