化简:f(a)=tan(-α-π)sin(-α-π)分之sin(α-2分之π)cos(2分之3π+α)tan(π-α)
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化简:f(a)=tan(-α-π)sin(-α-π)分之sin(α-2分之π)cos(2分之3π+α)tan(π-α)
写出具体步骤
写出具体步骤
首先你要先了解三角函数「广义角变狭义角」的原则:(1)90与270度正换余, 180与360函数不变(2)留意各三角函数在不同象限的正负 正弦与余割函数(sin/csc)在一二象限为正(三四象限为负) 余弦与正割函数(cos/sec)在一四象限为正(二三象限为负) 正切与余切函数(tan/cot)在一三象限为正(二四象限为负)可以参考看看附图,多想一想应该就通了比方说:sin(3π/2+α) PS.α先视为锐角的狭义角270度所以换为余弦cos(270度+α) 为第四象限角, 原先的sin值为负所以sin(3π/2+α)=-cosαf(a)=tan(-α-π)sin(-α-π) / sin(α-π/2)cos(3π/2+α)tan(π-α)tan(-π-α)= -tan(α)sin(-π-α)= +sin(α)sin(-π/2+α)= -cos(α)cos(3π/2+α)= +sin(α)tan(π-α)= -tan(α)f(a)=-tan(α)*sin(α) / -cos(α)*sin(α)*[-tan(α)] =-1/cos(α)=-sec(α)给你作个参考 广义角变狭义角sin(π/2-α)=cosαcos(π/2-α)=sinαtan(π/2-α)=cotαcot(π/2-α)=tanαsin(π/2+α)=cosαcos(π/2+α)=-sinαtan(π/2+α)=-cotαcot(π/2+α)=-tanαsin(π-α)=sinαcos(π-α)=-cosαtan(π-α)=-tanαcot(π-α)=-cotαsin(π+α)=-sinαcos(π+α)=-cosαtan(π+α)=tanαcot(π+α)=cotαsin(3π/2-α)=-cosαcos(3π/2-α)=-sinαtan(3π/2-α)=cotαcot(3π/2-α)=tanαsin(3π/2+α)=-cosαcos(3π/2+α)=sinαtan(3π/2+α)=-cotαcot(3π/2+α)=-tanαsin(2π-α)=-sinαcos(2π-α)=cosαtan(2π-α)=-tanαcot(2π-α)=-cotαsin(2kπ+α)=sinαcos(2kπ+α)=cosαtan(2kπ+α)=tanαcot(2kπ+α)=cotα(其中k∈Z)![](http://img.wesiedu.com/upload/3/f5/3f5a13f03e40db04cb9262ee0d51145f.jpg)
![](http://img.wesiedu.com/upload/3/f5/3f5a13f03e40db04cb9262ee0d51145f.jpg)
化简:f(a)=tan(-α-π)sin(-α-π)分之sin(α-2分之π)cos(2分之3π+α)tan(π-α)
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