Question

Solve the equation 2cos(x) - 1 = 0
Possible answers:
A. x = (π/6) + 2nπ and x = (5π/6) + 2nπ, where n is an integer.
B. x = (π/3) + 2nπ and x = (5π/3) + 2nπ, where n is an integer.
C. x = (π/4) + 2nπ and x = (5π/4) + 2nπ, where n is an integer.
D. x = (π/6) + 2nπ and x = (7π/6) + 2nπ, where n is an integer.
E. x = (2π/3) + 2nπ and x = (4π/3) + 2nπ, where n is an integer.

Answer 1

in the equation add 1 to both sides then divide by 2 to get this equation:

cos(x) = 1/2

now think of an angle such that when you take the cosine of that angle you get 1/2....

Answer 2

I'm not quite sure what you mean

Answer 3

Can you explain further or clarify?

Answer 4

do you have your unit circle?

Answer 5

yes

Answer 6

look at the common angles and see which angle gives a cosine of 1/2...

Answer 7

what coordinate does cosine refer to... the x coordinate or y coordinate?

Answer 8

I'm not sure. I don't have much practice with unit circles

Answer 9

look at page 3 here.... and tell me what angle corresponds to the x coordinate being 1/2...
http://tutorial.math.lamar.edu/pdf/Trig_Cheat_Sheet.pdf

Answer 10

K. Give me a second... my internet is slow.

Answer 11

It looks like both 300 degrees and 60 degrees have an x coordinate of 1/2