The process is correct, assuming that any point on L 1 (x 1, y 1) is the reciprocal of L2 and the straight line is L4, then the intersection of L4 and L2 is the symmetry point; It is also the midpoint, and then the symmetrical position (x3, y3) on L3 (x 1, y 1) can be calculated, and then the linear equation can be solved by two points.

In fact, there are formulas: K 1, K2, which are the linear slopes of L 1, L2 respectively; α and β are l 1 respectively, and the included angle of L2 is

K 1=tanα，K2=tanβ，K=tan[(α+β)/2]，

In fact, K2 can be solved by the formula tan(α+β) of the sum of two angles, which is not very complicated.

k2 =-(K * K * K 1+2K-K 1)/(K * K+2K * K 1+ 1)

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