[The leftmost x-coordinate is  and the rightmost
x-coordinate is .  They are partly cut off in
the picture above.]


The period of a function is the distance along the x-axis
from the beginning of a figure until it starts repeating 
same figure

The round hump figure starts at  and ends (and
starts over at . That's a distance along the x-axis
of  =  =  = 
So its period is .

You can always get the period by subtracting the x-coordinate
at the beginning of any repeating figure from the x-coordinate
at the end of the repeating figure.

You could also get the period from the beginning and end of the
second round hump figure:

 =  =  = 

or from the beginning and end of the third hump:

 =  = 

or from the fourth hump

 =    <--the easiest way to find the period!

or the fifth or sixth hump.

Edwin