The zeros of (the values of x where sin x = 0) are at the multiples of and it is there that the graph crosses the x-axis. has a maximum value of at and a minimum value of at and all angles coterminal with them.
The values of sin x regularly repeat themselves every units. Thus, sin x has a period of (360 degrees).
Now, means there are 2 periods in an interval of
Finally, in , the 2 means that in an interval of length , there are 2 periods. There will be 2 occilations every . The period will be or .