If the normal to the curve $x^{2/3}+y^{2/3}=a^{2/3}$ makes an angle $\theta$ with the $x$-axis then the slope of the normal is

Question

$$\begin{array}{1 1}(1)-\cot\theta&(2)\tan\theta\\(3)-\tan\theta&(4)\cot\theta\end{array}$$