Thread: find points on a circle

If I know the coordinates of the centre of a circle and its radius, how do I find other points on the circle?

(-not including the perfect "north,south,east,west positions")

(-not using simple trig: [sin theta * r] and [cos theta * r], then add those to x,y of centre)

TYIA

Originally Posted by hello

If I know the coordinates of the centre of a circle and its radius, how do I find other points on the circle?

(-not using simple trig: [sin theta * r] and [cos theta * r]...

Center of circle at (a,b)

Given an arbitrary x coordinate, need to find y:

r^2 = (x-a)^2 + (y-b)^2
x^2 -2xa + a^2 = (y-b)^2 - r^2

The LHS contains the unknown.
x^2 -2xa - (y-b)^2 + r^2 + a^2 = 0
Solve the quadratic.