Basic inverse trigonometric function

$\arcsin(x)=y\Longrightarrow \sin(y)=x$ by using the fact $\sin(y)=\cos(\frac{\pi}{2}-y)$ , $\cos\left(\frac{\pi}{2}-y\right)=x\Longrightarrow \arccos(x)=\frac{\pi}{2}-y$ $y=\frac{\pi}{2}-\arccos(x)$ $\arcsin(x)=\frac{\pi}{2}-\arccos(x)$ $\arcsin(x)+\arccos(x)=\boxed{\frac{\pi}{2}}$

Maderchod nots pad

Just substitute by any value for x, you will get $\dfrac{\pi}{2}$ .