Find all solutions of the equation in the interval [0, 2)π

Question

Find all solutions of the equation in the interval [0, 2)π

2cos0+1=0

Write your answer in radians in terms of π

If there is more than one solution, separate them with commas.

Answer 1

2cosT = 0

cosT = 0/2=0

T = cos^-1(0) = pi/2 or 3pi/2

T= pi/2, 3pi/2