Question

Which of the following is a solution to 4cos2x − 1 = 0?

A. 60°
B. 150°
C. 210°
D. 330°

Answer 1

A. 60*

Explanation:

I used the website M A T H W A Y . C O M

and I remember learning this in my school, I worked this problem by hand and am confident that A is the correct answer.

Answer 2

60°

A is correct

Explanation:

Given:
`4\cos^2x-1=0`

`4\cos^2x=1`

Divide by 4

`\cos^2x=(1)/(4)`

Taking square root both sides

`\cos x=\pm (1)/(2)`

`\cos x=(1)/(2)` or
`\cos x=-(1)/(2)`

`x=\cos^(-1)((1)/(2))` or
`x=\cos^(-1)(-(1)/(2))`

`x=60^\circ,300^\circ` or
`x=120^\circ,240^\circ`

Hence, x=60° is correct