Question

In the (x, y) coordinate plane, what is the radius of the circle described by the equation `(x - 3)^2 + (y + 6)^2=sqrt15`?

Answer 1

The given equation is the equation of a circle with center at `(3,-6)` and radius `root(4)15=1.968`.

Explanation:

It is apparent from the equation's LHS that the square of distance of the point `(x,y)` from `(3,-6)` is always `sqrt15` (on the RHS).

Hence, the given equation is the equation of a circle with center at `(3,-6)` and radius `sqrt(sqrt15)` or `root(4)15=1.968`.