ClipArt ETC
The three points in which any line cuts the sides of a triangle and the projections, from any point in the plane, of the vertices of the triangle on to the same line are six points in involution.

Involution

The three points in which any line cuts the sides of a triangle and the projections, from any point…

Illustration of a polygon with a diagonal drawn. A diagonal of a polygon is a line joining the vertices of two angles not adjacent (AC).

Polygon With Diagonal

Illustration of a polygon with a diagonal drawn. A diagonal of a polygon is a line joining the vertices…

Orthogonal projection of a closed plane-faced polyhedron.

Polyhedron

Orthogonal projection of a closed plane-faced polyhedron.

Orthogonal projection of a closed plane-faced polyhedron.

Polyhedron

Orthogonal projection of a closed plane-faced polyhedron.

An illustration of a sphere cut into polygons as bases with their vertices at the center of sphere.

Sphere Cut Into Pyramids.

An illustration of a sphere cut into polygons as bases with their vertices at the center of sphere.

Illustration to show lines drawn from the vertices to join at a point within the triangle.

Triangle With Lines From the Vertices That Join a Point Within

Illustration to show lines drawn from the vertices to join at a point within the triangle.