POINT • CIRCLE • LINE
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A Line Is Tangent To A Circle, A Point Independently
Number of solutions: 3
GeoGebra construction
Steps
- First, choose the circle of inversion so that the given point is its center.
- Apply the inversion to the given line and the given circle.
- Since the given point, being the center of the inverting circle, is mapped to infinity, the solution circles appear as common tangents to the images of the inverted objects.
- Invert the found tangents back to obtain the solution circles.
- The problem has three solutions.
GeoGebra construction
Steps
- Create a line p2 that will pass through the center of S1 and the given point A. Name the intersection of the circle k1 and the line p2 closer to point A B and find the center C between points A and B.
- Draw a perpendicular line p3 that is perpendicular to the line p1 and passes through the given point A.
- Find points equidistant from the circle k1 and point A. Thus, we are looking for a hyperbola d with foci at points A and S1 that passes through point C.
- We look for points equidistant from the line p1 and point A. Thus, we are looking for a parabola c with a control line p1 and foci at point A.
- Name the intersections of the hyperbola e and the parabola g S.
- The points S are the centres of the circles we are looking for. They must all pass through point A.