Question

Which of the following are solutions to the equation 2cos2x - 1 = 0? Check all that apply.

Answer 1

is it just D?

Answer 2

B. 2

Answer 3

B and D?

Answer 4

B.
Transpose -1 to the other side.
It will become 2cos^2x=1
Divide both sides by 2
cos^2x=1/2
square root both side
cosx=square root of 1/2
x= arccos of (square root of 1/2)
x=45 degrees.
Answer is B. -7pi/4 is just equal to -315 degrees which is also equal to 45 degress

Answer 5

A also