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三角恒等式,就证题的基本途径来说,和代数恒等式是完全一致的,但它有自己的特点,概括起来,有以下几点值得函授学员注意: 1.在进行三角恒等变形时,应先把三角式中的各三角函数化为同角(化复角为单角),同名函数(一般化为正弦和余弦函数),然后再利用有关公式进行推证。 2.如果三角恒等式中只含有正切、余切的三角函数,一般可利用它们的倒数关系和代数恒等变形法则来证明,不必再化为正弦和余弦函数。
Trigonometric identity is exactly the same as the algebraic identity in terms of the basic approach of the test question, but it has its own characteristics. To sum up, there are the following points worthy of correspondence with the trainees: 1. In the trigonometric constant deformation, First, each trigonometric triangle function is transformed into the same angle (a compound angle is a single angle), the same name function (generalized as a sine and cosine function), and then the relevant formula is used to infer. 2. If the trigonometric identities contain only tangent and cotangent trigonometric functions, they can generally be proved by their reciprocal relations and the law of algebraic constant deformation. They do not need to be converted into sine and cosine functions.