Find the absolute minimum of f(x)=sin(x)-cos(x) on [0,pi]
The Attempt at a Solution
I know the answer is 0 from looking at a graph, but I cannot figure out how to express my workings algebraically. The end goal of this is to do a presentation on how I figured out the answer and I don't think I can really just get up and draw a graph on sin(x)-cos(x) and then just point at 0. So far I've managed to get the first derivative and find x=-pi/4. From here I just don't know what to do.