More Than 800 Geometry Articles, Theorems, Problems

But, although there is no study which presents so simple a beginning as that of geometry, there is none in which difficulties grow more rapidly as we proceed.
Augustus De Morgan
On The Study And Difficulties Of Mathematics, Dover, 2007

What Is Geometry?
What Is Analytic Geometry?

The site includes more than 800 articles on various K12 topics in geometry and solved geometric problems. The geometric contents of the site can be accessed in the alphabetic order of page titles, or through specialized searches listed below:

3-4-5 Triangle9 Point CircleAltitude
Angle bisectorBook of lemmasButterfly theorem
Carpets theoremCeviansCircumcircle
CollinearityComplete quadrilateralConcyclicity
ConstructionsCoordinatesCyclic quadrilateral
Euler lineEye opener seriesFallacies
Golden ratioHomothetyImpossible Shapes
IncircleInscribed angleInversion
Isoperimetric theoremMedial triangleMenelaus' theorem
Morley's theoremNeusis constructionsOrthic triangle
Paper foldingParallelogramPoint at Infinity
Poles and polarsPorismProjective property
Pythagorean theoremReflectionRotation
SangakuSimson lineStereographic Projection
TangentsTranslation
 
... and much much more ...

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