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锐角三角函数是初中数学的重要内容,也是中考的热点之一.求锐角的三角函数值方法较多,下面举例介绍求锐角三角函数值的几种常用方法,供参考.一、定义法当已知直角三角形的两条边,可直接运用锐角三角函数的定义求锐角三角函数的值.例1如图1,在ABC中,∠C=90°,AB=13,BC=5,则sin A的值是()(A)513(B)1213(C)512(D)135分析题目中已知∠A的对边BC和斜边AB的长,可直接运用锐角三角函数的定义求解.
An acute trigonometric function is an important part of junior high school mathematics, but also one of the hottest points in the exam.How to find the trigonometric value of the acute angle method is more, the following examples of several commonly used methods for seeking acute trigonometric function for reference. For both sides of a right triangle, we can directly use the definition of trigonometric trigonometric function to find the value of acute trigonometric function. Example 1 As shown in Figure 1, in ABC, ∠C = 90 °, AB = 13, BC = 5, then sin The value of A is () () 513 (B) 1213 (C) 512 (D) 135 The length of the opposite edge BC and hypotenuse AB of the known ∠A in the analysis subject can be solved directly using the definition of acute trigonometric function.