With all trig functions, the period can be calculated with the equation PB = 2π.
P = period
B = anything in the tangent part of the equation except the x. (in this case, it would be 6)
When we plug in 6 for B, we get 6P = 2π.
Divide both sides by 6 and you get P = 2π / 6
OR
P = π/3
