The voltage of a generator

A generator gives a peak of $300\ \text{V}$. Its coil can turn $20$, $40$ or $80$ times a second. You will make the program find the time of one cycle for each, the number of cycles in $0.1\ \text{s}$ at $40\ \text{Hz}$, and the voltage $5\ \text{ms}$ after the start at $20\ \text{Hz}$. Then it draws the three waves.

The idea. One cycle takes $T = \dfrac{1}{f}$. The voltage is $V = V_0 \sin(2\pi f t)$.

Your tasks.

1. Inside the loop, work out T_ms, the time of one cycle in milliseconds at the frequency f.
2. Find cycles, the number of cycles in $0.1\ \text{s}$ at $40\ \text{Hz}$.
3. Find v5, the voltage at $t = 0.005\ \text{s}$ when $f = 20\ \text{Hz}$.