Can someone please show me the process of answering this question?
By writing sin3X as sin(2X+X), show that sin3X=3sinX−4sin^3X
I know that sin2X=2sinXcosX and the other trig identities, but I cannot understand how to substitute it in, in particular the answer follows as:
sin3X = sin2XcosX + cos2XsinX - it is this step that I am struggling with!
Thanks