cyclictroll
New member
Ignorance is sad. 
I'm betting that not A SINGLE ONE OF YOU knows what a cyclic quadrilateral is without googling it. That is terrible. Stop believing in false conspiracies, and learn about the beauty of the universe.
All these are equivalent:
ABCD is cyclic
<ABC+<CDA=180
<BCD+<DAB=180
<ABD=<ACD
<BCA=<BDA
<BAC=<BDC
<CAD=<CBD
AD*BC=AB*CD+AD*BC (Ptolemy's, learn the inversion proof because the synthetic one is pretty ugly)
A,B,C,D are concyclic
I'm betting that not A SINGLE ONE OF YOU knows what a cyclic quadrilateral is without googling it. That is terrible. Stop believing in false conspiracies, and learn about the beauty of the universe.All these are equivalent:
ABCD is cyclic
<ABC+<CDA=180
<BCD+<DAB=180
<ABD=<ACD
<BCA=<BDA
<BAC=<BDC
<CAD=<CBD
AD*BC=AB*CD+AD*BC (Ptolemy's, learn the inversion proof because the synthetic one is pretty ugly)
A,B,C,D are concyclic
