tg(x-\frac{\pi}{2})=1
tg(x-\frac{\pi}{2})=tg\frac{\pi}{4}
x-\frac{\pi}{2}=\frac{\pi}{4}+k\pi
x=\frac{\pi}{4}+\frac{\pi}{2}+k\pi
x=\frac{3}{4}\pi+k\pi