Question

1. Rewrite with only sin x and cos x.

sin 3x - cos x

Answer 1

sin3x-cosx
=sin(2x+x)-cosx
=sin2x*cosx+sinx*cos2x-cosx
=2sinx*cos^2(x)+sinx*(cos^2(x)-sin^2(x))-cosx
=3sinx*cos^2(x)-sin^3(x)-cosx

Answer 2

Using the following formulas
sin(a+b)=sina*sinb+cosa*cosb
sin2x=2sinx*cosx
cos2x=cos^2(x)-sin^2(x)