If y=y(x) satisfies the differential equation x d y+(x tan (y/x)-y) d x=0, x>0, and y(1)=(π)/2, then a value of y(√ 2 ) is

If $\displaystyle y=y(x)$ satisfies the differential equation $\displaystyle x d y+\left(x \tan \left(\frac{y}{x}\right)-y\right) d x=0, x>0$, and $\displaystyle y(1)=\frac{\pi}{2}$, then a value of $\displaystyle y(\sqrt{2})$ is