Locus of Centres of Circles Tangent to a Fixed Circle

Locus of Centres of Circles Tangent to a Fixed Circle

For a fixed circle with centre $$o$$ and radius $$r$$, centres of circles of fixed radius $$r$$ externally tangent to it satisfy:

$$OP=R+r$$

Usage

- Converts a circle-tangency condition into a locus equation for the centre.