Need help confusing problem Solve trig Equation:
2cosxcos2x+sinxsin2x+cosx=0

I can seem to break it down and use the correct identities)

Question

Need help confusing problem Solve trig Equation: 
2cosxcos2x+sinxsin2x+cosx=0

I can seem to break it down and use the correct identities)

tkhunny · Answer

What have you tried?

I thought this was cute:

2cosxcos2x+sinxsin2x+cosx=0
cosxcos2x+cosxcos2x+sinxsin2x+cosx=0
cosxcos2x+(cosxcos2x+sinxsin2x)+cosx=0
cosxcos2x+(cos(x-2x))+cosx=0
cosxcos2x+cos(-x)+cosx=0
cosxcos2x+cos(x)+cosx=0
cosxcos2x+2cos(x)=0
cosx(cos2x+2)=0

Of course, if you really meant $\cos^{2}(x)$ and not $\cos(2x)$ then that's another story.

tkhunny · Answer

It is amazing how much better one can respond to a question when the entire question is presented.  It's even better when you show your work!