Q. If $z = \sec^{- 1}{\left( \frac{x^{4} + y^{4} - 8x^{2}y^{2}}{x^{2} + y^{2}} \right),\ \ \ then\ x\frac{\partial z}{\partial x} + y\frac{\partial z}{\partial y\ }}\$is equal to

A) $\cot z\$
B) $2\cot z$
C) $2\tan z$
D) $2\sec z$
Explanation

(b)
Given, $\sec{z = \frac{x^{4} + y^{4} - 8x^{2}y^{2}}{x^{2} + y^{2}}}$
Here, $n = 2$
$\therefore x\frac{\partial z}{\partial x} + y\frac{\partial z}{\partial y} = 2.\frac{\sec z}{\sec{z.\tan z}} = 2\cot z$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.