Express 4sinx-cos(pi/2 - x) as a single trignometric function

The cos(pi/2-x) is equivalent to sinx because the cosx graph is just the sinx graph but shifted to the left by a phase difference of pi/2 radians, and cos(pi/2 - x) is also shifting the cosx graph to the right by pi/2 radians which just transforms it into a sinx graph. We can rewrite this as 4sinx-sinx and this therefore just becomes 3sinx.