- 123

- 0

**1. The problem statement, all variables and given/known data**

I need to find [tex] \rho((4,2), A_2)[/tex] where [tex]A_2=\{(x,y)|x^2+y^2=1 \} [/tex].

**2. Relevant equations**

**3. The attempt at a solution**

I know that the definition says that this distance is the greatest lower bound of [tex] \{\rho(x,a)|a \in A\}[/tex]. So the distance between [tex]\rho((4,2), (x,y))= \sqrt{(x-4)^2+(y-2)^2}=\sqrt{x^2+8x+16+y^2-4y+4}= \sqrt{21-8x-4y}[/tex] and then I am not sure what to do.