Question

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

Answer 1

Answer:

60°

A is correct

Step-by-step explanation:

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

$4\cos^2x=1$

Divide by 4

$\cos^2x=\dfrac{1}{4}$

Taking square root both sides

$\cos x=\pm \dfrac{1}{2}$

$\cos x=\dfrac{1}{2}$     or      $\cos x=-\dfrac{1}{2}$

$x=\cos^{-1}(\dfrac{1}{2})$    or    $x=\cos^{-1}(-\dfrac{1}{2})$

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

Hence, x=60° is correct

Answer 2

Answer:

A. 60*

Step-by-step 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.