# Stereographic projection from North Pole

Let there be a point *N* on a sphere that can be called North Pole. Let’s consider the projection (called stereographic) that maps to each point *P* of the sphere that is distinct to *N*, the intersection *Q* of the line *NP* with the tangent plane to the sphere in the South Pole (diametrically opposed to *N*).

We note that after such a transformation (which is the restriction of an inversion), the image of a circle is transformed into a circle.*The original figure was made by* **Luigi Tomasi**.