# Online Geometry: Rectangle, Theorems and Problems

Euclid's Elements, Book X, Lemma for Proposition 33 One page visual illustration.

Eyeball Theorem: Animated Angle to Geometry Study.
Chords and Rectangle.

Eight-Point Circle Theorem
Step-by-Step construction, Manipulation, and animation.

Mindpoints and Rectangle

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

Cyclic Quadrilateral: Ratio of the Diagonals
The ratio of the diagonals of any cyclic quadrilateral equals the ratio of the sums of the rectangles contained by the sides that share the diagonals' end points

Interactive Mind Map of the Van Hiele Model of Geometric Thought
Level 2. Abstraction: learners recognize relationships between types of shapes. They recognize that all squares are rectangles, but not all rectangles are squares.

Triangle and Squares 22
Rectangles of equal area.

Triangle and Squares 20
Rectangles of equal area.

Billiards and Geometry - Index
Billiards Table

Euclid's Elements Book I, 23 Definitions. One-page visual illustration.
Euclid's Elements Book. Index

Dynamic Geometry 1472.
Cyclic Quadrilateral, Perpendicular Diagonals, Rectangle, Step-by-step Illustration.

Dynamic Geometry 1452.
Japanese Theorem, Sangaku, Cyclic Quadrilateral, Incenter, Rectangle, Inradius. Step-by-step illustration using GeoGebra.

Geometry Problem 1439.
Rectangle, Diagonal, Perpendicular, Circles, Areas, Art, Poster, Typography, iPad Apps.

Geometry Problem 1400.
Triangle with three rectangles on the sides, Perpendicular Bisectors, Concurrency.

Geometry Problem 1396.
Triangle with three rectangles on the sides, Vertices, Perpendicular lines, Concurrency.

Geometry Problem 1395.
Triangle with three rectangles on the sides, Midpoints, Perpendicular lines, Concurrency.

Geometry Problem 1352.
Rectangles, Sum of Squared Distances.

Geometry Problem 1318.
Rectangle, Equilateral Triangle, Distances, Perpendicular, Measurement.

Geometry Problem 1198
Right Triangle, Square, Rectangle, Quadrilateral, Altitude, Equal Areas.

Geometry Problem 1195
Square, Two Rectangles, Congruence, Metric Relations.

Geometry Problem 1185
Similar Rectangles, Four Quadrilaterals, Sum of the Areas, Metric Relations.

Geometry Problem 1144.
Three Equal Squares, Diagonals, Perpendicular, 90 Degrees, Angle Bisector.

Geometry Problem 1070.
Circle, Chord, Equilateral Triangle, Square, Rectangle, Area, Diameter, Perpendicular.

Geometry Problem 1046.

Geometry Problem 989.
Arbelos, Semicircles, Diameter, Perpendicular, 90 Degree, Common External Tangent, Rectangle, Midpoint of Arc.

Geometry Problem 971.
Equilateral Triangle, Rectangle, Common Vertex, Sum of Right Triangles Areas.

Geometry Problem 969.
Equilateral Triangle, Rectangle, Common Vertex, Right Triangles Areas.

Geometry Problem 968.
Equilateral Triangle, Rectangle, Common Vertex, Midpoint.

Geometry Problem 868
Cyclic Quadrilateral, Circle, Five Rectangles, Four Centers, Congruence.

Geometry Problem 711.
Rectangle, Midpoint, Angle, Concyclic Points, Cyclic Quadrilateral.

Geometry Problem 866
Cyclic Quadrilateral, Circle, Rectangle, Center, Congruence, 90 Degrees.

Geometry Problem 620
Three Rectangles, Diagonals, Centers, Angles.

Geometry Problem 601

Problem 563.
Regular Pentagon, Center, Rectangle, Diagonals, Angle.

Problem 537.
Rectangle, Midpoints, Diagonal, Angle Bisector.

Proposed Problem 252.
Rectangle, isosceles right triangle, square, areas.

Proposed Problem 35.