Question

Solve 2cos^2x + cosx − 1 = 0 for x over the interval [0, 2 pi ).

Answer 1

@iGreen

Answer 2

Lol, I have no idea.

Answer 3

ok XD

Answer 4

Let \[x = \cos \theta\]
So you get \[2x^2+x-1=0\] can you finish it off ;)

Answer 5

But note, you don't want x, you want theta, so you have to remember your ratios and solve for cos theta = ... what ever you get.

Answer 6

is it -1,1/2

Answer 7

Yes, now you can solve for theta between your interval.

Answer 8

that makes no sense to me

Answer 9

Mhm? Now let cos theta = -1, and 1/2

Answer 10

since we have cos theta = x

Answer 11

i still dont get it

Answer 12

Can you be more specific

Answer 13

i dont know what you are talking about at all, all this cos jazz is confusing me

Answer 14

...

Answer 15

Confusion may come from your equation saying x, and me using theta, just switch it around, shouldn't matter

Answer 16

i dont get it ....

Answer 17

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