- Ryan Hirst
Desargues: →1) Pappus' Theorem 2) Vector notation: http://www.geogebratube.org/material/show/id/35213 3) Desargues' Theorem: http://www.geogebratube.org/material/show/id/35525
The Law of Sines.
- Hold the four rays fixed. Let (sinα sinδ)/(sinβ sinγ) = k, a constant. Then (AC∙BD)/(BC∙AD)=k, for every line which intersects the rays.
- Hold points A, B, C, D fixed. Let (AC∙BD)/(BC∙AD) =k, a constant. Now draw four rays through A, B, C, D from an arbitrary point. We will always have (sinα sinδ)/(sinβ sinγ)=k.