http://www.cut-the-knot.org/ctk/pww.shtml

http://www.sunsite.ubc.ca/LivingMathematics/V001N01/UBCExamples/Pythagoras/pythagoras.html

Just two examples, to explain what I was meaning.

And, JohnHaway, thank you for the explainations.
Not having English as a mother tongue, I can miss subtilities... for example, I learnt "guys and gals" here in Awad, but never encountered "guys" in a mixed sense.