Q: Let f(x)=20x-10sin(4x) for 0<=x<=pi/2 Find the largest interval(s) over which the function f is increasing or decreasing. I tried to solve this: f'(x)=20-40cos(4x) =20(1-2cos(4x)) on keeping f'(x)=0, i get x=pi/12 I just cannot get correct intervals to work properly with my online math homework s...