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构造法是重要的数学思想方法,在高考和模考中都有体现,它灵活多变,构思精巧,深受广大师生喜爱.但运用构造法要求学生基本功扎实,有较强的联想和应变能力,因而也成了教学的难点.本文谈谈突破难点的一些对策,以希指正.题1(2010年江苏高考题)已知ABC的三边长都是有理数.(1)求证:cos A是有理数;(2)对任意正整数n求证:cos n A也是有理
Constructive method is an important way of thinking and mathematics in college entrance examination and test have reflected, it is flexible, sophisticated design, loved by the majority of teachers and students.But the use of construction method requires students to have a solid basic work, strong association and adaptability Ability, and thus has become a teaching difficult.This article talk about some of the difficulties to overcome some of the countermeasures, to correct me .Question 1 (Jiangsu 2010 college entrance examination) is known ABC long sides are rational numbers. (1) Proof: cos A is a rational number; (2) For any positive integer n verify: cos n A is also reasonable