Question

Rewrite with only sin x and cos x.

cos 3x

Answer 1

helppppppppppppp:(

Answer 2

start with
\[\cos(3x)=\cos(2x+x)\] then use the "addition angle" formula for cosine

Answer 3

\[\cos(2x+x)=\cos(2x)\cos(x)-\sin(2x)\sin(x)\]
then use the "double angle" formula for sine and cosine to finish

Answer 4

im at cos 3x= cos (2x+x) = \[(\cos ^{2} x-\sin^2 x) \cos x - (2\sin x \cos x)(\sin x)\]

Answer 5

ok

Answer 6

you have done what is asked
your answer is in terms of \(\sin(x)\) and \(\cos(x)\)

Answer 7

you could maybe clean it up with some algebra

Answer 8

im not able to clean it up like i dont know how to simplify (2sinx cosx) (sinx )

Answer 9

\[-2\sin(x)\cos(x)\sin(x)=-2\sin^2(x)\cos(x)\]

Answer 10

and
\[(\cos^2(x)-\sin^2(x))\cos(x)=\cos^3(x)-\sin^2(x)\cos(x)\] via the distributive law

Answer 11

the answer choices are:
cos x - 4 cos x sin^2x

-sin^3x + 2 sin x cos x

-sin^2x + 2 sin x cos x

2 sin^2x cos x - 2 sin x cos x


literally nothign matches