A case of the 3-dimensional problem of Appollonius.
A characterization of all equilateral triangles in .
A generalization of a two triangle inequality.
A new butterfly curve. (Eine neue Schmetterlingskurve.)
A new proof of Morley's theorem
A note on -chordal polygons.
A note on ovals and their evolutoides.
A pair of general triangle inequalities.
A parametrization of equilateral triangles having integer coordinates.
A proof of Atiyah's conjecture on configurations of four points in Euclidean three-space.
A Synopsis of Elementary Results in Pure Mathematics [Book]
About a determinant of rectangular matrix and its geometric interpretation.
Achèvement de la démonstration géométrique élémentaire donnée par Steiner pour ce théorème : «le cercle possède la plus grande parmi toutes les figures planes isopérimètres»
Algebraic proofs for geometric statements.
Altitude, Orthocenter of a Triangle and Triangulation
We introduce the altitudes of a triangle (the cevians perpendicular to the opposite sides). Using the generalized Ceva’s Theorem, we prove the existence and uniqueness of the orthocenter of a triangle [7]. Finally, we formalize in Mizar [1] some formulas [2] to calculate distance using triangulation.
An Analogue of the Pythagorean Theorem with Regualr n-Gons instead of Squares.
An elementary proof of Blundon's inequality.
An elementary proof of the Theorem of Beckmann and Quarles.
An Upper Bound for the Minimum Diameter of Integral Point Sets.
Areas of certain polygons in connection with determinants of rectangular matrices.