what is the standard form of the equation of the circle with the center (1,2) and contains the point (1,0)?

Question

anonymous · Answer

since the center is $(1,2)$ you know it looks like 
$$(x-1)^2+(y-2)^2=r^2$$  to find $r^2$ find the square of the distance between $(1,2)$ and $(1,0)$   
the distance is pretty clearly $2$ since they have the same $x$ coordinate and the $y$ coordinates are two apart

anonymous · Answer

so the radius is 1 since the distance is the same as the diameter and half of the diameter would be 1?

anonymous · Answer

no the radius is 2, and so the square of the radius is 4