You can use the fact that sin(2x) - sin(x) = 2sin(x/2)cos(3x/2).
I'm having trouble manually working out points of intersection between trig graphs. I can do them when its between a cos graph and a sin graph using cos^2(x) + sin^2(x) = 1 but I cant do them when they are the same etc. sin x = sin 2x
How do you manually work these pts of intersection out? Do I have to use the general formula?