Question

we know that slope of x axis is 0 and slope of y axis is infinity and x and y are perpendicular to each other than why the product of slope is not -1?

Answer 1

$$\begin{gathered} \mathrm{Slope}\mathrm{of}\mathrm{x}\mathrm{axis}=\tan 0 \\ \mathrm{and}\mathrm{slope}\mathrm{of}\mathrm{y}-\mathrm{axis}=\tan 90 \\ \mathrm{So}\mathrm{product}\mathrm{of}\mathrm{slope}\mathrm{of}=\tan 0\times \tan 90 \\ =\tan 0\times \tan \left(90+0\right) \\ =\tan 0\times \left(-\cot 0\right) \\ =\tan 0\times \frac{-1}{\tan 0} \\ =-1 \end{gathered}$$