Question

How do you solve 2cosØ=-1 for 0<Ø<360degrees?

Answer 1

Can you help with another one? @CGGURUMANJUNATH

Answer 2

Can anyone help please?!

Answer 3

Can you help @CGGURUMANJUNATH?

Answer 4

start with
\[\cos(\theta)=-\frac{1}{2}\]

Answer 5

Divide each side by 2. You get cos x = -1/2. Look on the unit circle; which value has a cosine of -1/2?

Answer 6

2pi/3

Answer 7

then see if you can think of an angle or two that has that value for cosine
as @aurorablue01 said, look at the unit circle
the last page of the attached cheat sheet will help

Answer 8

and 4pi/3?

Answer 9

apparently you are supposed to give your answer in degrees
there are two answers in the interval

Answer 10

Oh, so it is 120 and 240?

Answer 11

yeah your two are right

Answer 12

Yes

Answer 13

Ok, thanks both of you.

Answer 14

You're welcome