Express the following in terms of sinx

Question

1). cosx (2cosx - 3tanx)

I need to use one or both of the following equations as these are the only ones we have been taught so far:

i). cos²x + sin²x = 1

ii). tanx = sinx / cosx

Answer 1

cosx(2cosx-3tanx)

cosx(2cosx-3[sinx/cosx])

2cos^2x-3cosx[sinx/cosx])

sin^2x+cos^2x=1 implies cos^2x=1-sin^2x

2(1-sin^2x)-3sinx

2-2sin^2x-3sinx

-2sin^2x-3sinx+2 is the answer