Determine the solution of the equetion: 2cos x-1=0? 2cos x=0? and 2cos x+1=0?

Answer 1

2cosx - 1 = 0
2cosx = 1
cosx = 1/2
I know from my basic trig relations that cos 60° = 1/2 and by the CAST rule cos 300° = 1/2
so x = 60° or x - 300° , or in radians: π/3, 5π/3

2cosx = 0
cosx = 0
I know from looking at a cosine curve that
x = 90° or x = 270° or in radians : π/2, 3π/2

do the third one the same way I did the first one

Answer 2

The answer is 120 if i'm not mistaken

Answer 3

Since the cosine is negative in quads II or III, the answers would be 120° or 240°