Here is something fun to look at for the weekend. It is a `proof’ in song by an Argentinian comedy singing troupe called Les-Luthiers. The video images are by someone else.

If you don’t know spanish, this might be an opportunity to decide to learn some.

Of course the proof is not a real proof. It starts well and it gets completely derailed, but it goes like many a proof in geometry: one adds a whole bunch of auxiliary lines and circles and voila.

In Spanish speaking countries the theorem in the song is called Thales theorem. The other one of inscribed angles is also ascribed to Thales, so they are both Thales’ theorems. In English speaking countries the attribution is different for the theorem in the song.

on January 10, 2009 at 7:11 amLuboš MotlHola David, do I understand well that the science content of the nice song is complete crap?

OP+PQ=ST? On the picture, O,P are pretty much “heights” while T is a “width”.

Moreover, the real theorem of Thales says that all angles built above/inside a half-circle are 90 degrees. ;-)

If I am right, is this the method how Argentine people like Juan learned their maths? :-)

on January 10, 2009 at 2:33 pmdberensteinHi Lubos:

Of course the proof is not a real proof. It starts well and it gets completely derailed, but it goes like many a proof in geometry: one adds a whole bunch of auxiliary lines and circles and voila.

In Spanish speaking countries the theorem in the song is called Thales theorem. The other one of inscribed angles is also ascribed to Thales, so they are both Thales’ theorems. In English speaking countries the attribution is different for the theorem in the song.