Question

Solve cos(x)(cosx+1)=0

@terenzreignz :)

Answer 1

answer choices A,B,C,D from top to bottom :)

**I'm not too sure, but I'm leaning towards A... what do you think? :)

Answer 2

Same technique..., even though it's not really necessary, replace cos(x) with u
u(u+1) = 0
Possible values for u?

Answer 3

0, -1 ?

Answer 4

Yup.... so
cos(x) =0
cos(x) =-1
Possible values for x?

Answer 5

pi, pi/2, 3pi/2, and 2pi ?

Answer 6

or 90, 180, 270, 360 degrees?

Answer 7

2pi?
\[\Large \cos(2\pi) = 1\]

Answer 8

yup! 1=1 :)

Answer 9

We don't have a \(\large \cos(x) = 1\)

Answer 10

im not following :( what do u mean?

Answer 11

\(2\pi\) is not a solution...
Because we only have
cos(x) = 0
and
cos(x) = -1

We do NOT HAVE
cos(s) = 1

Answer 12

okay... so whats next then? :/

Answer 13

cos(x) *

Answer 14

What's next? You have not even finalised your answer for the current step...
What are the values for x which would make
cos(x) = 0
or
cos(x) = -1
true?

Answer 15

lol yeah haha i didn't mean like the next step haha i meant like how can i figure this part out.. :P lol sorry bout that! :P

so do i plug pi, pi/2, 3pi/2 into cos(x) and see if they equal 0 or -1? and not 2pi tho right?

Answer 16

yeah, so, are the answers \(\Large \pi \ , \ \frac{\pi}{2} \ , \frac{3\pi}{2}\) correct?

Answer 17

i believe so... they are, aren't they? :)

Answer 18

I'm asking you.
I'm asking you to be sure.

Answer 19

cos(pi)= -1

cos(pi/2) = 0

cos(3pi/2) = 0

so yeah right?

sorry i probs should have included this part in the thing above lol :P

Answer 20

Okay. Good enough. So your final answer?

Answer 21

B ?

Answer 22

Yeah.
Current Streak : 0
Best Streak : 3

You were leaning towards A... so... nope :P

Answer 23

hahah yeah :( back to 0 :(

lol but yay! :) this one makes sense now tho!!! :) thanks!! :)