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Smallest Enclosing Circle

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The smallest circle that encloses a set of given circles can be computed using a variant of Welzl’s algorithm. Instead of testing whether a circle contains a point, test whether a circle contains another circle; likewise instead of computing the circle that intersects two or three points, compute the circle that has internal tangents to two or three circles. (The latter is Apollonius’ problem.)

Drag the circles to see the enclosing circle change.