# Solve this

If $u={\mathrm{sin}}^{-1}\left(\frac{{x}^{2}+{y}^{2}}{x+y}\right)$

Prove that $x\frac{\partial u}{\partial x}+y\frac{\partial u}{\partial y}=\mathrm{tan}u$

If $u={\mathrm{sin}}^{-1}\left(\frac{{x}^{2}+{y}^{2}}{x+y}\right)$

Prove that $x\frac{\partial u}{\partial x}+y\frac{\partial u}{\partial y}=\mathrm{tan}u$