怎么解这个题---**Question 24** **Question Stem:** 如图, AB是⊙O的直径, 点C在⊙O上, CD与⊙O相切, AD∥BC, 连接 OD, AC. (1) 求证: ∠B=∠DCA; (2) 若 tan B = (√5)/2, OD = 3√6, 求⊙O的半径长. **Mathematical Formulas/Equations:** tan B = (√5)/2 OD = 3√6 **Chart/Diagram Description:** * **Type:** Geometric figure showing a circle and lines. * **Main Elements:** * A circle with center O. * Line segment AB is the diameter of the circle, passing through O. Points A, O, and B are on a horizontal line. A is to the left of O, and B is to the right of O. * Point C is on the upper semi-circle. * Line segment AC is drawn. * Line segment BC is drawn. * Line segment CD is drawn, which is tangent to the circle at point C. Point D is outside the circle. * Line segment AD is drawn. * Line segment OD is drawn. * There is an annotation AD || BC, indicating that the line segment AD is parallel to the line segment BC. * Angles are formed by the intersections of these lines and segments. **Other Relevant Text:** 第5页 (共8页)