Question

How do you prove this without having to change the left side?

`sin4x = 8cos^3sinx-4cosxsinx`

Answer 1

`LHS=sin4x`

`=2sin2xcos2x`

`=4sinxcosx(2cos^2x-1)`

`color(red)(["using formula "sin2x=2sinxcosx and cos2x=2cos^2x-1])`

`= 8cos^3sinx-4cosxsinx=RHS`