令y=sina-1,x=cosa-2 (sina)^2+(cosa)^2=1 (x+2)^2+(y+1)^2=1 则f(a)=y/x 即是斜率Ky=Kx 圆心(-2,-1),半径=1 圆心到切线距离等于半径 Kx-y=0 d=|-2k+1|/√(k^2+1)=R=1 4k^2-4k+1=k^2+1 3k^2-4k=0 k=0,k=4/3 则:f(a)(...