Question

HELP PLEASE!!!

Find all solutions to the equation.

cos2x + 2 cos x + 1 = 0

Answer 1

Factor it.

Answer 2

Set each factor equal to 0 and solve.

Answer 3

cos2x + 2cosx + 1 = 0

2(cosx)^2 - 1 + 2cosx + 1 = 0

2(cosx)^2 + 2cosx = 0

2 ( cosx )(cosx + 1 ) = 0

cosx = 0 or cosx = -1

so, x = π / 2 or x = 3π / 2 or x= π

hope this helps

Answer 4

Try this http://answers.yahoo.com/question/index?qid=20080205153101AAowpnU

Answer 5

Did you mean cos(2x) or cos^2x?

Answer 6

\[\cos ^2x+2\cos x+1=0\]

Answer 7

Is that the problem? Or is it this:

Answer 8

\[\cos( 2x)+2\cos x+1=0\]

Answer 9

cos^2x+2cos x+1=0

Answer 10

Thank you all for your help!

Answer 11

Np

Answer 12

Well then:
\[\cos ^2x+2\cos x+1=0\]

Answer 13

\[(\cos x+1)(\cos x+1)=0\]

Answer 14

\[\cos x+1=0\]

Answer 15

\[\cos x=-1\]

Answer 16

\[x=\pi +2\pi n\]