cos(π/2+α)=-sinα ,tan(π/2+α)=-cotα, cot(π/2+α)=-tan
诱导公式。
推导过程如下:sin(π/2+α)= cos α
sin(π+α) =sin[π/2+(π/2+α)]= cos(π/2+α)
又sin(π+α) = - cosα)
所以:cos(π/2+α)=-sinα
以下的也一样。
cos(π/2+α)=cosπ/2cosα-sinπ/2sinα=-sinα
tan(π/2+α)=sin(π/2+α)/cos(π/2+α)=cosα/(-sinα)=-cotα
cot(π/2+α)=cos(π/2+α)/sin(π/2+α)=-sinα/cosα=-tanα
cos(π/2+α)=sin[π/2-(π/2+α)]=sin(-α)=-sinα
sin(π/2+α)=cos[π/2-(π/2+α)]=cos(-α)=cosα
tan(π/2+α)=sin(π/2+α)/cos(π/2+α)=cosα/-sinα=-cotα
cot(π/2+α)=cos(π/2+α)/sin(π/2+α)=-sinα/cosα=-tanα