Question

Please help?!!!! I need some help!

Answer 1

What do you need help with?

Answer 2

@GoldPhenoix

Answer 3

Isn't that part of a test or exam?

Answer 4

its part of an assignment yes but dont give me the answer just how to start it of

Answer 5

It's Pre-Calculus what would i do use the unit circle?

Answer 6

I do not know Pre-Calculus. Sorry. =/ Ask someone else.

Answer 7

no problem thanks

Answer 8

let cos x=u . . After doing that, look at the equation. Isn't it now a quadratic equation? Factor it. Then revert u back to cos x. Lastly, do the same thing in solving for the zeroes of a quadratic equation...

Answer 9

@SkydexKiwi

Answer 10

ok let me see so
\[u ^{2}x+2ux+1=0\]

Answer 11

ahm, there's something wrong with that..

You will substitute u to cosx..

u= cos x

Answer 12

oh\[u ^{2}+2u+1=0\]

Answer 13

Yep.. That's the starting point... Next, Factor them...

Answer 14

so (u+1)(u+1)
u=-1

Answer 15

before you solve for the zeroes, you must revert u back to cos x...

Answer 16

(cosx+1)(cosx+1)

Answer 17

cosx=-1?

Answer 18

Now, when will cos x be equal to -1? What value of x will cos x be equal to -1?

Answer 19

would it be the third choice?

Answer 20

no, if you look at them the factors are the same..

How about trying to substitute values of x in cos x?
For example,
if x=0
cosx
cos (0)
cos (0) = 1

or
if x = pi/2

cos x
cos (pi/2)
cos (pi/2) = 0

Try them:)

Answer 21

what would cos^2 0 equal? would it be 0

Answer 22

uhm, we've reached the point where we've said that cosx = -1 ... Are you familiar to the cosine function??

Now we need to find that x... How about trying to substitute all that was in the choices? It'll be easier but too much work:)

Answer 23

cos(2pi)=i got .993993116
cos(pi)= .998497
i keep getting .99 or 1

Answer 24

how did you plug it in i just multiplied 2 and pi and then used the cosine button

Answer 25

@darkprince14

Answer 26

@satellite73 could you please help