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高中《代数》第一册P115,第17题,已知tgα=2,求(sinα+cosα)/(sinα-cosα)的值。此题虽浅显简单,但对学生培养能力、发展智力、引起兴趣,能起到相当的作用。我在讲完同角三角函数的基本关系式一节后,就此题并围绕它上了一节习题课。一题多解提问:上一节课布置的已知tgα=2,sinα、cosα的值各等于多少?同学们都解得sinα=±(2 5~(1/2))/5,cosα=±5~(1/2)/5。随即要大家练习P115。第17题,同学
High School Algebra Volume 1 P115, Item 17, known tgα=2, find the value of (sinα+cosα)/(sinα-cosα). Although this question is simple and simple, it can play a considerable role in cultivating students’ abilities, developing intelligence, and generating interest. After I had finished the basic relational equations of the synchromesh trigonometric function, I followed this question and wrote a series of exercises on it. Questions and answers to many questions: What is the value of tgα=2, sinα and cosα in the previous lesson? The students have solved sinα=±(2 5~(1/2))/5, cosα= ±5~(1/2)/5. Then we must practice P115. Question 17, classmates