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K
y=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)(max)4/3
f(a)(min)=0(x+2)^2+(y+1)^2=1 ？令y=sina-1,x=cosa-2∴sina=y+1,cosa=x+2∵(sina)^2+(cosa)^2=1∴(x+2)^2+(y+1)^2=1