The locus of point of intersection of perpendicular tangents drawn to ${\mathrm{x}}^2=4\mathrm{ay}$ is
 

$$\begin{gathered} The locus of point of intersection of perpendicular \tan gents \\ drawn to {\mathrm{x}}^2=4\mathrm{ay} is its directrix \end{gathered}$$

Directrix is parallel to x-axis and below x-axis 

$$\begin{gathered} \mathrm{y}=-\mathrm{a} \\ \mathrm{y}+\mathrm{a}=0 \end{gathered}$$