How to calculate a point with an given center, angle and radius?

Question

In this SO question, someone asked for calculating an angle from three points. I need to do the opposite thing.

I want to draw a clock, and I have tiny tick images.

Answer 1

In mathematics, to calculate the Cartesian coordinates from the polar coordinates:

x = r * cos(A) + x0;
y = r * sin(A) + y0;

where (x0, y0) is the centre of your circle, r is the radius and A is the angle.

But that assumes the mathematics coordinate convention i.e. x increases as you move rightwards, y increases as you move upwards. This is the default for views on Mac OS X Cocoa but I don't know if it is the same on the iPhone.

Also angles start at 3 o clock and go anti-clockwise i.e. 3 o clock is 0 degrees, 12 o clock is 90 degrees, 9 o clock is 180 degrees and 6 o clock is 270 degrees.

Also, the C sine and cosine functions work in radians.