Question

Rewrite with only sin x and cos x.

sin 3x



2 sin x cos^2x + cos x

2 sin x cos^2x + sin^3x

sin x cos^2x - sin^3x + cos^3x

2 cos^2x sin x + sin x - 2 sin^3x

Answer 1

(sinx)(cos2x)+(cosx)(sin2x)

Answer 2

(sinx)[(cosx)^2 - (sinx)^2] + (cosx)[2(sinx)(cosx)]

Answer 3

@Data_LG2
how do I go from here?

Answer 4

check this, it's the same thing:
http://openstudy.com/study#/updates/50f3105ee4b0694eaccf7977

Answer 5

None of the answers are applicable

Answer 6

@FutureMathProfessor
I edited the question to make the answers applicable

Answer 7

shouldn't the first option be
2 sin x cos^2x + sin x ?

Answer 8

nah... forget about me...

Answer 9

the fourth option is correct

Answer 10

How do you get that?

Answer 11

since \[\sin3x=\sin(x+2x)\]we use double angle formula to get\[\sin(x+2x) = sinxcos2x+cosxsin2x\]using the double angle formula again\[sinx(\cos^{2}x-\sin^{2}x) + cosx(2sinxcosx)\]since \[\cos^{2}x - \sin^{2}x = 1-2\sin^{2}x\]then ,\[sinx(1-2\sin^{2}x)+2sinxcos^{2}x\]expanding out the bracket will give you\[sinx-2\sin^{3}x+2sinxcos^{2}x\]

Answer 12

Do you understand it?

Answer 13

Thank you, I was using the wrong identity the whole time

Answer 14

You really helped me out a lot

Answer 15

haha... good luck with these kinda questions