## Archive for October, 2006

### A conic classification. Nine-point ellipse.

Saturday, October 28th, 2006

A classification of a conic through three no colinear given points, according the position of its center. Nine point ellipse.

### Art and Geometry

Friday, October 27th, 2006

### The maximal inscribed and the minimal circumscribed ellipse for a centrally symmetric convex figure.

Tuesday, October 24th, 2006

In this note we study the maximal inscribed and the minimal circumscribed ellipse of a cenrally symmetrc convex figure F and we prove two theorems between the area and the remarcable elements of the figure.

### Bistrot

Sunday, October 15th, 2006

### Convex figures with conjugate diameters.

Sunday, October 15th, 2006

The convex figure K has conjugate diameters if and only if its symmetroid K* is an affine image of a Radon curve

### The tree

Sunday, October 8th, 2006

### The triangle of minimum perimeter circumscribed to a smooth closed compact convex curve (c) in the plane.

Sunday, October 8th, 2006

Theorem

For the triangle T of a minimum perimeter circumscribed to a convex figure (c) the excircles of T are tangent to (c).

### The bird

Monday, October 2nd, 2006

### Van den Berg’s Theorem

Monday, October 2nd, 2006

Let Q(z)=z3+a1z2+a2z+a3=0 be a cybic in C and  z1,z2,z3 the roots denoted in the plane by the points A,B,C. The Steiner ellipse in the triangle ABC is denoted by E and F1, F2 the foci. Van den Berg’s theorem asserts that the roots of the derivate Q'(z) are the complex numbers defined in C by the points F1 and F2.