We have to solve the equation 2cos(3x) -1 for values in the interval 0=< x =< pi.

Now we see that 2cos(3x) -1 is not an equation, let's equate it to zero.

2cos(3x) -1 = 0

=> 2 cos 3x -1 = 0

=> 2 cos 3x = 1

=> cos 3x = 1/2

in the given t=interval we see that cos 60= 1/2

=> cos 3x = cos 60

=> 3x = 60

=> x = 20 degrees.

Therefore the required result is x = 20 degrees.

Given the equation 2cos(3x) -1 = 0

We need to solve for x if  0=< x =< pi.

==> 2cos(3x) -1 = 0

We will add 1 to both sides.

==> 2cos(3x) = 1

Now we will divide by 2.

==> cos(3x) = 1/2

Then we know that:

3x = pi/3

Now we will divide by 3.

==> x = pi/9