sin除以cos等于tan。
证明:在直角三角形中,设θ 为任意角,y为对边,x为邻边,r为斜边,由定义可知:
sinθ = y/r
cosθ = x/r
tanθ = y/x
所以:
tanθ = y/x
= (y/r)/(x/r)
= sinθ/cosθ
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角度制下的角的表示:
sin (α+k·360°)=sinα(k∈Z)
cos(α+k·360°)=cosα(k∈Z)
tan (α+k·360°)=tanα(k∈Z)
cot(α+k·360°)=cotα (k∈Z)
sec(α+k·360°)=secα (k∈Z)
csc(α+k·360°)=cscα (k∈Z)