I was doing a physics problem today and I needed to find when some movement is accelerating and when it is decelerating. So after some calculations, I got the equation I needed. I know that it is correct because when plotted, I can see from graph that I got the expected solution.
Unfortunately I don't know how to actually start solving the inequality. It looks like $$k \sin\left(\frac {\pi x} {2}\right)\cos\left(\frac {\pi x} {2}\right)>0$$ where $k$ is some huge sausage which is constant and positive.