POINT • CIRCLE • CIRCLE

Two Circles With Inner Contact, Point On The Smaller Circle

Number of solutions: 1

GeoGebra construction

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Steps

  1. Given are the circles a and b such that a is internally tangent to b. Also given is the point A, which lies on a and is not the tangent point of the two circles.
  2. Draw any circle c with A as its origin.
  3. Invert this circle. Point A' is now at infinity. The inverted forms of a and b shall be named a' and b' respectively.
  4. Now, construct the line d that is tangent to b' and parallel to a'. This line must touch a' and go through A' in infinity.
  5. Invert d around c. The resulting circle is the solution.

GeoGebra construction

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Steps

  1. Find the centres of the given circles
  2. The first set of points is the line h containing the given point A and the centre of the smaller circle S2
  3. Draw a line g containing the given point A and the center of the larger circle S1
  4. Find the intersections with the line g and the larger circle and name it D
  5. Draw a point F in the middle of the line AD
  6. Construct an ellipse with foci at point A and S1
  7. Find the intersection of the ellipse and the line h that is not point S2 and name it G
  8. Draw a circle k with centre G passing through point A