Math CentralQuandaries & Queries


Question from mikee, a student:

find the equation of a circle tangent to the circle x2+y2=4 and with the center at (0,5)

Hi Mikee,

The circle \[x^2 + y^2 = 4\]

has center $(0,0)$ and radius $\sqrt{4} = 2.$ I drew a diagram.


What is the radius of a circle with center $(0,5$ and tangent to the circle in the diagram? What is its equation.

Why does the problem say "find the equation of A circle..." rather than "find the equation of THE circle..."? Is there more than one answer?


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