Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. In geometry, an inverse curve of a given curve C is the result of applying an inverse operation to C. Specifically, the inverse with respect to a fixed circle with center O and radius k the inverse of a point Q is the point P for which P lies on the ray OQ and OP·PQ = k2. The Inverse of the curve C is then the locus of P as Q runs over C. The point O in this construction is called the center of inversion, the circle the circle of inversion, and k the radius of inversion. An inversion applied twice is the identity transformation, so the inverse of an inverse curve with respect to the same circle is the original curve. Points on the circle of inversion are fixed by the inversion, so the it''s inverse is itself.