CIRCLE • CIRCLE • CIRCLE

Three Externally Tangent Circles

Number of solutions: 2

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Steps

  1. We have circles c, d and h, which are all touching externally.
  2. Find points D, E and F, in which the circles intersect each other.
  3. Construct 3 hyperbolas, which have their foci in the circles' centers and cross through one of the points D, E and F, which are located on the circles, whose centers are foci of hyperbolas ?
  4. Find points S, where all three hyperbolas intersect.
  5. Construct lines p, which intersect with an S point and one of the circles' centers and find points I and N, which are an intersection of a p line and a circle through whose center p crosses.
  6. Construct circles k, which have their center in point S and also intersect either point I or N.

GeoGebra construction

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Steps

  1. Draw a circle k4 with centre S4 at the point of contact of two circles, which touches the third one.
  2. Represent the given circles by the circular inversion according to k4, resulting in the parallel lines c´ and d´ and the circle h´
  3. Draw the h-axis of the resulting parallel lines.
  4. Construct the circles k5 and k6 tangent to the two parallels and the circle h´
  5. Represent the resulting circles by circular inversion to obtain the resulting solutions, circles p´ and q´.