Question

2 cos 3x - 1 = 0

Answer 1

2cos 3x=1
Work it like any other equation

Answer 2

cos (3x) = 1/2
We know that cos(x) =1/2 when x = Pi/6, so it must be Pi/18

Answer 3

How did you get this? Im still a bit confused :(

Answer 4

Solve 2cos(3x)-1=0 for cos(3x)
this gives you: cos(3x)=1/2
as software said previously, we know that cos(x)=1/2 @ x=pi/6
Using this x=pi/6, replace x with 3x: 3x=pi/6 (solve for x)
Voila, x=pi/18; depending on your interval (ie 0<x<pi)