Graphing a Trig Function

[Aesiir]

the function is

f(x) = 3 cos [ x - (pi/2) ]

The problem that I have is with the period. I know that in y=AcosBx the period is 2pi/B but I don't quite know how to take it out of the [ x - (pi/2) ].

Also, I'd like to know what the period does exactly.
Why is it significant and what do I do with it on the graph?

 

[Darwin]

Haven't done maths for a long time but I'll try:
f(x) = 3 cos [ x - (pi/2) ]
f(x) = 3cosx - 3cos(pi/2)
since cos(pi/2) = 0,
f(x) = 3cosx
you should know how to graph this func

 

[Sypherz]

The period is the length between the two crowns of the sinusoid.

 

[Aesiir]

Darwin, I'm looking for the PERIOD. How to find the period by just looking at the equation

Sypherz, I don't need a definition, I need a way to find it.

Anyways, I was able to find the period... It's 2*pi.

 

[Imagine]

The subtraction doesn't affect the period, it just shifts the graph so that it looks like the graph of 3sinx