Find radius of a circle from intersecting chords Say I have two chords that intersect inside a circle, not at a right angle, and neither is the diameter. It seems to me this is enough information that the circle must be unique, but I can't seem to find the radius. 

Let $x$ be the known distance between circle center and point of chords intersection.
You must search for the useful / relevant property.
$$OB \cdot OD = OA\cdot OC = P$$
By property of intersecting chords ( segments product P= a known constant)..
$$ (R+x)(R-x)=P $$

from which radius of circle $R$ can be found
$$ R= \sqrt{x^2 + P}. $$
