数学大神求救！tan(X+90)还有tan(X-90)等于什么啊？ tan(90°-x)可以转换成什么？
1/10:1/15=(x+90):(x-90)\u600e\u4e48\u89e3\uff1f\u89e3:1/10:1/15=\uff08x+90\uff09:(x-90)
1/10*(x-90)=1/15*(x+90)
1/10x-90*1/10=1/15x+1/15*90
1/10x-1/15x=6+9
1/30x=15
x=15*30
x=450
tan(90\u00b0-x)=cotx
解答过程如下：利用奇变偶不变，符号看象限得tan（x+90）=—cotx
tan（x—90）=—tan（90—x）
=—cotx
分别等于-cotx和-cotx
tan(x+90)=sin(x+90)/cos(x+90)=cosx/(-sinx)=-cotx
tan(x-90)=sin(x-90)/cos(x-90)=-cosx/sinx=-cotx
tan（x+90°）＝－cotx
tan（x－90°）＝tan（90°+x）＝－cotx
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