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其实只是简化了一下计算方式,但是比原化减方法简单直观了太多。

AB=(x1x2)2+(y1y2)2AB2=(x1x2)2+(y1y2)2AB2(x1x2)2=(x1x2)2+(y1y2)2(x1x2)2ABx1x2=(x1x2)2(x1x2)2+(y1y2)2(x1x2)2AB=1+k2x1x2\begin{array}{ll} AB &= \sqrt{(x_1-x_2)^2+(y_1-y_2)^2}\\\\ AB^2 &= (x_1-x_2)^2+(y_1-y_2)^2\\\\ \frac{AB^2}{(x_1-x_2)^2} &= \frac{(x_1-x_2)^2+(y_1-y_2)^2}{(x_1-x_2)^2}\\\\ \frac{|AB|}{|x_1-x_2|} &= \sqrt{\frac{(x_1-x_2)^2}{(x_1-x_2)^2}+\frac{(y_1-y_2)^2}{(x_1-x_2)^2}}\\\\ |AB| &= \sqrt{1+k^2}|x_1-x_2| \end{array}

啊啊啊mathjax渲染以后跟我写的不一样!!! 查了一下是要把换行用的\\改成\\\\(二次转义