calculate x,y positions in circle every n degrees

x = radius *  cos(angle)
y = radius *  sin(angle)

Inverse Y-axis:

x = radius *  sin(angle)
y = radius * -cos(angle)

If radians is used then

radian = angle * 0.0174532925

and

x = radius *  cos(radian)
y = radius *  sin(radian)

Radian is the standard unit of angular measure, any time you see angles, always assume they are using radians unless told otherwise.