Question

What is the frequency of the sinusoidal graph?

Answer 1

The frequency $f$ is defined as

$f = \dfrac{1}{T}$

where $T$ is the period, i.e. the time between two maximum/minimum points.

In your example, you can see that a maximum is reached when $x = 0$, and the next one at $x = \pi$. This means that the period is

$T = \pi-0 = \pi$

So, the frequency is

$f = \dfrac{1}{\pi}$