I can't solve this for the life of me and I am sure I will feel like an idiot after seeing the solution. Any help would be greatly appreciated before I pull my hair out over this little problem! Argh!
verify the identity:
sin4x = 8cos"cubed"xsinx - 4cosxsinx
if any help, I tried factoring out 4cosxsinx leaving 2cos"squared"x - 1, however I didn't get too far into this before getting stuck.. :)