2x-y-3=0
y=2x-3
C(a,2a-3)
r^2=(a-3)^2+(2a-3+2)^2=(a-5)^2+(2a-3-2)^2
a=2
C(2,1),r^2=10
C:(x-2)^2+(y-1)^2=10
y=(x/2)+m
x-2y+2m=0
d^2=|2-2*1+m|^2/5≤r^2
-5√2≤m≤5√2sina+cosa=3/5,cos(π/2+2a)等于=sin(2a)=-16/25