A formula for a circle

Answer 1

In the coordinate plane:

(x - a)2 + (y - b)2 = r2 where the centre of the circle is at (a, b) and the radius is r.

In parametric form, it is

x = a + r*cosΦ

y = b + r*sinΦ

where 0 ≤ Φ < 360 deg.