Equation to determine radius for a circle that should intersect a given point? Simple question. I tried Google but I don't know what search keywords to use.
I have two points on a $2D$ plane. Point 1 $=(x_1, y_1)$ and Point 2 $=(x_2, y_2)$.

I'd like to draw a circle around Point 1, and the radius of the circle should be so that it intersects exactly with Point 2.

What is the equation to determine the required radius?

The radius is simply the distance between the two points.  So use the standard Euclidean distance which you should have learned.
