Inversion is a one-to-one transformation of the points of the plane (except one point) by means of a given circle (circle of inversion). We shall call this circle C, of radius r and centre q. The center of the circle of inversion (center of inversion) has no image.

If the center of the circle of inversion is the origin and the radius is 1 this transformation has a simple formula:

In the general case, this mapping is given by:

The points on the circle of inversion transform into themselves and each point inside the circle is transformed to a point outside the circle (and vice-versa). Each point, its image and the center of the circle of inversion are in the same line. Sometimes we call this transformation as reflection in a circle.

Each line through the center of inversion is transformed in the same line.

Each line not passing through the center of inversion is transformed in a circle through the center of inversion.

The inverse of a circle is a straight line or a circle. It is a line if the circle passes through the center of inversion.

The image of a circle not passing through the center of inversion is another circle not passing through the center of inversion.

MORE LINKS

Complex Polynomial Functions(1): Powers with natural exponent

Complex power functions with natural exponent have a zero (or root) of multiplicity n in the origin.

Complex Polynomial Functions(2): Polynomial of degree 2

A polynomial of degree 2 has two zeros or roots. In this representation you can see Cassini ovals and a lemniscate.

Complex Polynomial Functions(3): Polynomial of degree 3

A complex polinomial of degree 3 has three roots or zeros.

Complex Polynomial Functions(4): Polynomial of degree n

Every complex polynomial of degree n has n zeros or roots.

Complex Polynomial Functions(5): Polynomial of degree n (variant)

Every complex polynomial of degree n has n zeros or roots.

Cero and polo (Spanish)

Podemos modificar las multiplicidades del cero y del polo de estas funciones sencillas.

Cero and polo (variant) (Spanish)

The Complex Exponential Function

The Complex Exponential Function extends the Real Exponential Function to the complex plane.

The Complex Cosine Function

The Complex Cosine Function extends the Real Cosine Function to the complex plane. It is a periodic function that shares several properties with his real ancestor.

Multifunctions: Powers with fractional exponent

The usual definition of a function is restrictive. We may broaden the definition of a function to allow f(z) to have many differente values for a single value of z. In this case f is called a many-valued function or a multifunction.

Multifunctions: Two branch points

Multifunctions can have more than one branch point. In this page we can see a two-valued multifunction with two branch points.

Taylor polynomials: Complex Exponential Function

The complex exponential function is periodic. His power series converges everywhere in the complex plane.

Taylor polynomials: Complex Cosine Function

The power series of the Cosine Function converges everywhere in the complex plane.

Taylor polynomials: Rational function with two complex singularities

We will see how Taylor polynomials approximate the function inside its circle of convergence.