Points on a circle

You will test whether points lie on a circle, using the distance from its centre.

Your tasks.

1. In on_circle, return True when the point p is at distance r from centre, and False if not. Allow a tiny error: compare with abs(... - r) < 1e-9.
2. In count_on_circle, return how many of the points lie on the circle.
3. Set n_on to how many of the six listed points lie on the circle with centre $(0, 0)$ and radius $5$. Use your function.