Apollonius' problem using equations of tangent circles
Tangent conic sections to the graph of a function are used to solve the Apollonius' problem. The statement of the Apollonius' problem can originate ten types of the problem. Here, three types are solved. Namely, three lines (LLL), one line and two points (LPP) and three circles (CCC). These three combinations consider the three objects: circle, line and point. The solution strategy is similar in the other seven cases of the problem. When the objects, line or circle, are part of the elements of the problem, the line or circle are taken as functions. The equations of the tangent circles in the form center-radius are applied to these functions. Since the unknown tangent circle is tangent to the other objects (or passes through the eventual given points) of the problem, the different equations produce a system of non-linear equations. From the solution of this system of equations can be obtained the center-radius of the unknown tangent circle and the points of tangency. When a point is an element of the problem, the equation of the (tangent) circle must contain this point.
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