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At this site you will find mathematical subjects I investigated. All pages are in English. Some pages are also available in Dutch. When a change of language is possible it is shown at the top of the page.
Chris van Tienhoven, the Netherlands
Op deze site vindt u enige wiskundige onderwerpen waar ik onderzoek naar gedaan heb. Alle pagina’s zijn in het Engels. Sommige pagina’s zijn ook in het Nederlands. Wanneer er een taalkeuze is, dan staat dit bovenaan de pagina d.m.v. een (NL-)vlag.
Chris van Tienhoven, Nederland
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Main Topics:

In Triangle Geometry we studied everything connected with 3 points / 3 lines.
However there are also points connected with 4 points / 4 lines.
For example there is a centroid in a figure with 4 points.
There is a point with least sum of squared distances to 4 lines.
There are lots of surprises.
For example the centroid in a figure of 4 points differs from the centroid in a figure of 4 lines.
When you are interested go to the  Encyclopedia of Quadri-Figures .
QA-QG-QL-Centroids-01                                         QA-P1                                               QG-P4                                                          QL-P12

  What are Perspective Fields ? 

Look at the resemblance between these 3 pictures:  


Why are there so many collinearities in Triangle Geometry?
Challenged by this question I developed a theory on Perspective Fields.