已知圆上一点坐标P(x,y),圆心坐标O(0,0),半径为R,怎么求旋转X角度后的P'坐标?

已知圆上一点坐标P(x,y),圆心坐标O(0,0),半径为R,怎么求旋转X角度后的P'坐标?

旋转前：x=Rcosa y=Rsina
逆时针旋转X角度后：x'=Rcos(a+X) y'=Rsin(a+X)
x'=R(cosacosX-sinasinX)
=RcosacosX-RsinasinX
=xcosX-ysinX
y'=R(sinacosX+cosasinX)
=RsinacosX+RcosasinX
=ycosX+xsinX
所以旋转后P'(xcosX-ysinX,ycosX+xsinX)

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