Question

How do I find sin2x+cosx=0, using a double angle or half angle? I got 11pi/6, 3pi/2, 7pi/6, pi/2.

Answer 1

But I got the answers wrong so idk what to do.

Answer 2

well use sin(2x) = 2sin(x)cos(x)

so the equation becomes

2sin(x)cos(x) + cos(x) = 0

now factor

cos(x)(2sin(x) + 1) = 0

hope it helps you get a solution.

Answer 3

Thats exactly what I did but my answers came out wrong @campbell_st

Answer 4

so you have

cos(x) = 0 and sin(x) = -1/2

Answer 5

yup @campbell_st

Answer 6

I just graphed it and got those solutions.... so I really can't help. It could be a mistake in the answers provided or a typo in the question.

Answer 7

Its ok thnx anyway @campbell_st