Parallelogram, Theorems and
Problems  5




Triangle and Squares. 21
theorems. Visual illustrations. 

Generalizing Van Aubel: Michael de Villiers' Theorems.


Eyeball Theorem:
Animated Angle to Geometry Study.


Hippocrates and Squaring the Circle


Triangle with Squares
Problem


Thébault's Theorem. Parallelogram with Squares theorem


Varignon and Wittenbauer parallelograms. Quadrilateral: midpoints and
trisection points of the edges.


Van Aubel's Theorem.
Quadrilateral with Squares. Proof with animation.


Ptolemy's Theorem.


Cyclic
Quadrilateral: Ratio of the Diagonals


Sangaku Problem. The
incenters of four triangles in a cyclic quadrilateral form a rectangle. 

Proposed
Problem 35.
Incenters and Inradii in Cyclic Quadrilateral. 


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