# Math Help - Point along a circle

1. ## Point along a circle

I am trying to find a point along a circle (see the picture).

R - is the radius of the circle (known)
C - is the length from the edge of the circle to the centre (known)
d - is a known distance from the centre, along C

I need to know the point along the dish arc distance "d" away from the centre at a right angle to C

Any help?

thanks

2. If I'm reading the question properly, the point that you're looking for is independent of C isn't it ? You're simply off-setting from a vertical diameter by a distance d.
Call your point P and run a horizontal to Q on the vertical diameter. Then, if the centre of the circle is O, $OQ^{2}+QP^{2}=OP^{2}.$
That is, $OQ^{2}=R^{2}-d^{2}.$