SHM from a point on a circle

You will write the equation of simple harmonic motion as functions, and use them to follow the foot of a point that goes round a circle.

The idea. A point moves round a circle of radius $A$ with the period $T$. Its foot on a diameter is at $x = A\cos(\omega t + \phi)$, where $\omega = 2\pi/T$.

Your tasks.

1. In angular_frequency, return $\omega$ for the period T.
2. In position, return $x$ at the time t.
3. In track, return a list of n positions, taken at equal steps through one period, starting at $t = 0$ with $\phi = 0$.