I need help with this question. I just don’t understand it.

Answer:
The frequency of the sinusoidal wave is, [tex]\frac{2}{\pi}[/tex]
Step-by-step explanation:
The frequency of a sine wave function states that the number of cycle it will completes in every second.
The formula for frequency:
[tex]frequency = \frac{1}{Time period}[/tex]
From the given graph:
Time period = [tex]\frac{\pi}{2}[/tex]
then;
[tex]frequency = \frac{1}{\frac{\pi}{2}}=\frac{2}{\pi}[/tex]
Therefore, the frequency of the sinusoidal wave is, [tex]\frac{2}{\pi}[/tex]