Question

Rewrite with only sin x and cos x.

sin 3x - cos x (6 points)

Select one:
a. 2 sin x - sin3x - cos x
b. 2 sin x cos2x + sin x - 2 sin3x - cos x
c. 2 sin3x cos4x + 1
d. 3 sin x cos x - sin3x - cos x

Answer 1

sin(3x) = sin(x + 2x)

= sinx cos(2x) + cosx sin(2x)

= sinx [1 - 2sin2x] + cosx [2sinxcosx]

= sinx - 2sin3x + 2cos2xsinx