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圆周角是连结圆和其他几何图形的纽带,其定理及推论对于角的计算、证明角相等、弧、弦相等等问题,提供了十分重要的方法,但圆周角定理的发现与证明却是教学中的一大难点.笔者通过对教材的研读和学情的分析,将本节课的难点确定为当圆心在圆周角外部时,圆周角定理的证明.学生在尝试证明这种情况时,往往不能明确研究的对象,即找不准
The circle angle is the link between the link circle and other geometrical figures. The theorem and inferences provide very important methods for the calculation of angles, equal proof angles, arcs, and chord phases. However, the finding and proof of the theorem of the circumferential angle is teaching. One of the major difficulties. The author through the study of the teaching material and the analysis of the situation, the difficulty of this lesson is determined as when the center of the circle outside the corner, the proof of the theorem of the circumference angle. Students try to prove this situation, often The object of the study cannot be clearly identified.