algorithm for finding out pixel coordinates on a circumference of a circle

Question

how do i find out pixel value at certain degree on the circumference of a circle if I know the pixel co-ordinates of the center of the circle, radius of the circle ,and perpendicular angle. Basically, I am trying to draw the hands of a clock at various times ( 1 o clock , 2 o clock etc )

Answer 1

Let h be the hour as a floating point number (h=2.25 would be 02:15, etc.) between 0 and 12. (cX,cY) are the coordinates of the center. hLength and mLength are the lengths of the hour and min hands.

// Hour hand
hAngle = 2.0*Pi*h/12.0; // 0..12 mapped to 0..2*Pi
hX = cX + hLength * sin(hAngle);
hY = cY - hLength * cos(hAngle);

// Min hand
mAngle = 2.0*Pi*h; // 0..1 mapped to 0..2*Pi, etc.
mX = cX + mLength * sin(mAngle);
mY = cY - mLength * cos(mAngle);

Answer 2

Where the centre of the circle is (X0, Y0), the radius is R and the angle with the x-axis is theta:

X1 = (R * cos theta) + X0

and

Y1 = (R * sin theta) + Y0

Answer 3

If (x1,y1) is a point on the circumference and (x,y) is the center, then x1 = x + r * cos(angle) and y1 = y + r * sin(angle)

Answer 4

if center is at x0, y0, and 0,0 iz at bottom-left corner, then 1 o'clock is at x0 + rsin(2π/3), y0+rcos(2π/3).

Answer 5

Draw lines from the center to coordinates computed with sin for the y coordinates and cos for the x coordinates (both multiplied by the length of the hand).

Wikipedia has more information on how sin and cos "work".