Find the locus of intersection of two perpendicular tangent to the hyperbola $\large\frac{x^2}{a^2}-\frac{y^2}{b^2}$$=1$?

Question

$\begin{array}{1 1}(a)\;h^2+k^2=a^2-b^2\\(b)\;h^2+k^2=a^2+b^2\\(c)\;h^2-k^2=a^2-b^2\\(d)\;k^2-h^2=a^2-b^2\end{array}$