Physics

Problem

A unit incident vector is

\mathbf{s}=\tfrac{4}{5}\,\hat{\mathbf{i}}+\tfrac{3}{5}\,\hat{\mathbf{j}}

and the corresponding unit reflected vector is

\mathbf{r}=\tfrac{4}{5}\,\hat{\mathbf{i}}-\tfrac{3}{5}\,\hat{\mathbf{j}}

. Find a unit normal vector to the reflecting plane that makes an acute angle with

\mathbf{s}