圆心角与圆周角是与圆有关的两个重要的角,二者不同,但它们又好像一对孪生兄弟,关系非常密切.在解决与圆有关的角的计算问题时,往往有十分重要的作用.一、利用圆心角或圆周角求角1.利用圆心角求圆周角例1(2013年湛江卷)如图1,AB是⊙O的直径,∠AOC=110°,则∠D=().A.25°B.35°C.55°D.70°解析:由于∠AOC=110°,所以∠BOC=70°,于是∠D=35°.选B. The central angle and the circumferential angle are two important corners related to the circle, and they are different, but they are like a pair of twin brothers and they are closely related. It is often very important to solve the problem of computing the circle-related corners 1, the use of central angle or circumferential angle of the angle 1. The use of the central angle for the circumferential angle Example 1 (Zhanjiang 2013) Figure 1, AB is ⊙ O diameter, ∠ AOC = 110 °, then ∠ D = ( ). A.25 ° B.35 ° C.55 ° D.70 ° Resolution: Since ∠AOC = 110 °, so ∠BOC = 70 °, so ∠D = 35 °.