According to the vertical diameter theorem and pythagorean theorem. Solution: Connect ab⊥cd. OA According to the vertical diameter theorem, point E is the midpoint of AB, AE= AB=5, OE=OC-CE=OA-CE.

According to Pythagorean Theorem, OA2=AE2+OE2=AE2+(OA-CE)2,

The solution is OA= 13, so CD=2OA=26, that is, the diameter of the circle is 26.