Menu of inversive macros

These simple macros were written to avoid the need to repeat very basic constructions when building pictures for inversive geometry. Of course, Cabri has the built-in command inverse, which gives the inverse of a point in a circle.

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touching Given a point A on a circle C and a point B not on C, draws the i-line through B touching C at A. tangent Given a point A on a circle C, draws the tangent to C at A. circumcircle Given three distinct points, draws the unique i-line through all of them. invertcircle Given circles C and D, draws the inverse of C in D - note the order! invertline Given a circle C and a line L, draws the inverse of L in C.

Warning these macros are not robust - if the construction requires a point on a circle,
you must choose a point on the circle. Otherwise you will get false results.

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