# math question (1 Viewer)

#### highkeydropout

##### Member
cos2x=1 (0,2pi)
hey guys would i include 0 and two pi as reference angle or just 0, keep getting confused on how to do it. thanks!

#### idkkdi

##### Well-Known Member
cos2x=1 (0,2pi)
hey guys would i include 0 and two pi as reference angle or just 0, keep getting confused on how to do it. thanks!
wdym, what are you trying to do? what is the question bruh. is (0,2pi) the domain?

• highkeydropout

#### Everwinter

##### Member
I also don't quite understand your question, but if you are solving for x. Firstly consider α = 2x, then times the domain by 2, i.e. [0, 4π] or 0 ≤ α ≤ 4π, then solve for cos α = 1 in this domain, the answer is: α = 0, 2π, 4π. i.e. 2x = 0, 2π, 4π ⇒ x = 0, π, 2π.

You can also solve this graphically, you first draw the graph of cos 2x, which is cos x that dilate horizontally by a factor of 1/2 in the domain of [0, 2π] (the graph contract), then you draw the line y = 1, and find the solutions for x.

#### highkeydropout

##### Member
wdym, what are you trying to do? what is the question bruh. is (0,2pi) the domain?
solve in the domain (0, 2pi)

#### idkkdi

##### Well-Known Member
solve in the domain (0, 2pi)
parentheses ( ) means exclude, brackets [ ] mean include.
e.g.
(1.2]
domain is from 1 to 2 excluding 1 including 2.