If $z= \sec^{-1} \bigg(\large\frac{x^4+y^4-8x^2y^2}{x^2+y^2}\bigg)$ then $x \large\frac{dz}{dx}$$+ y \large\frac{dz}{dy}=$

Question

\[\begin {array} {1 1} (1)\;\cot z & \quad (2)\;2 \cot z \\ (3)\;2 \tan z & \quad (4)\;2 \sec z \end {array}\]

Answer 1

$(2)\;2 \cot z$