Find all solutions of the equation 2cos x Squareroot 2 0 S

Find all solutions of the equation. 2cos x - Squareroot 2 = 0 Select the correct answer, where k is any integer: a. pi/5 + 2k pi, 4pi/5 + 2k pi b. pi/5 + 2k pi, 9pi/5 + 2k pi c. pi/4 + 2k pi, 7pi/4 + 2k pi d. pi/4 + k pi, 7pi/4 + k pi

Solution

2cos x - sqrt2=0

cos x=1/sqrt2

x=cos^-1(1/sqrt2)

x=pi/4 +2k pi , 7pi/4 +2k pi

correct option is c