在与圆的有关计算和证明题中,经常会涉及到圆心.但是许多同学往往对圆心的认识和重视不够,很容易忽视“圆心是直径的中点”这一基本性质,导致解题陷入困境.下面列举两例.例1如图1,AB是☉O的直径,CD是弦,AE⊥CD于点E,BF⊥CD于点F,若AB= Often in the calculation and proof of the circle, the center of the circle is often involved, but many students often do not know enough about the center of the circle and can not easily overlook the basic nature of “the center of the circle is the diameter” and lead to solution Example 1 As shown in Figure 1, AB is ☉ O diameter, CD is a chord, AE ⊥ CD at point E, BF ⊥ CD at point F, if AB =