我们知道,点P(x,y)关于直线y=x的对称点为(y,x);关于y=-x的对称点为(-y,-x);关于x=a的对称点为(2a-x,y);关于y=b的对称点为(x,2b-y).这些都是关于轴对称的特殊情形.若轴是一般情况则通过设两对称点为P(x,y)和P′(x′,y′),利用PP′的中点在轴直线上和这两点连线的斜率与轴直线斜率互为负倒数这两个关系来解决的.下面给出轴是一般情况下求对称点的一个公式,供大家参考. 设关于直线l∶y=kx+b对称的两对称点为P(x,y)和P′(x′,y′),其中k=tgα We know that the symmetry point of the point P(x,y) for the line y=x is (y,x); the point of symmetry for y=-x is (-y,-x); the point of symmetry for x=a is (2a-x,y); The symmetry point for y=b is (x,2b-y). These are all special cases of axisymmetric. If the axis is a general case, then by setting two symmetry points to P(x, y) and P′(x′, y′), using the relationship between the slope of the middle point of PP′ on the axis line and the two points and the slope of the axis line are negative reciprocals, the following is given. The axis is a formula for finding the symmetry point in general, for your reference. Let two symmetrical points symmetrical about the line l:y=kx+b be P(x,y) and P’(x’,y’), where k=tgα