Question

Find all solutions to the equation.

cos2x + 2 cos x + 1 = 0

Answer 1

double angle formula
cos 2x = 2cos^2 x - 1

Answer 2

I dont understand whats the next thing to do to solve the problem?

Answer 3

once you make the substitution, factor it then solve for x

Answer 4

so i substitute a letter in for cos? like y?

Answer 5

no...

Answer 6

\[\cos 2x = 2\cos^2 x - 1\]

Answer 7

you substitute cos 2x for 2cos^2 -1

Answer 8

Okay so I get cos^2 x = cos2x. What do I do next

Answer 9

no...
cos 2x = 2cos^2 -1

Answer 10

2cos^2x -1

Answer 11

Oh okay do i solve for x? I'm confused what im solving for here

Answer 12

first make the substitution and show me what you get

Answer 13

Im confused you said to substitiute cos 2x for 2cos^2 -1 but I did that and you said it was wrong

Answer 14

I don't know what to do can you walk me through it what do I substititue for what?