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三角函数是初中阶段解直角三角形的重要工具,对于一些特殊的三角函数,例如30°、45°、60°,都可以通过特殊角度的直角三角形来求其三角函数的值.而对于15°和75°这样的三角函数,由于未学到高中的半角、倍角公式,所以解决起来有一定的困难.本文拟通过构造含15°角的直角三角形,介绍15°角正切值的不同求法,以达到启迪学生,提高解题能力的目的.
Trigonometric functions are important tools for solving right-angled triangles in junior high school. For some special trigonometric functions, such as 30 °, 45 ° and 60 °, trigonometric functions can be obtained by the right-angled triangles with special angles. For trigonometric functions of 15 ° and 75 ° trigonometric function, it has some difficulties to solve because it does not learn the half-angle and double-angle formula of high school.This paper intends to introduce the different method of 15 ° tangent by constructing a right-angled triangle with 15 ° angle so as to achieve Inspire students to improve the ability to solve problems.