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高中代数第一册中关于C_(α+β)的证明,是利用单位圆表示角的终边上的点的坐标,构造两个“相等”的圆心角,由相等的圆心角所对弦相等及两点间的距离公式完成的。证明简练且具有一般性。但是,由于其证法不蹈常规,虽说学生可以接受,然而,为什么要这样做?这种证法是怎样想到的?学生只知其然,不知其所以然。在实际教学中,多数教师往往只要求学生记住公式,会正确使用就行了。至于公式的证明,尤
The proof of C_(α+β) in the first volume of algebra algebra is to use the unit circle to represent the coordinates of the point on the end of the angle, constructing two “equal” center-circle angles, which are equal to each other by equal central angles. The distance formula between the two points is completed. Proven and general. However, because the proof is not the same, although the students can accept it, why should this be done? How does this kind of proof come to mind? The student only knows the truth, and I do not know why. In practical teaching, most teachers only require students to remember formulas and they will use them correctly. As for the proof of formula, especially