Problem A. 446. (February 2008)
A. 446. The lengths of tangents drawn from the points A, B and C to a sphere s are a, b and c, respectively. T is a point on the sphere, not co-planar with A, B and C, such that .
Prove that the sphere passing through the points A, B, C, T touches s.
Deadline expired on March 17, 2008.