\int_0^{2-x}\cos\left(\frac{\pi}{2}y\right) \mathrm{d}y=\frac{2}{\pi}\sin\left(\frac{\pi}{2}y\right)\Big\vert_0^{2-x}=\frac{2}{\pi}\left[\sin\left\{\frac{\pi(2-x)}{2}\right\}-\sin{0}\right]