matthen:

Unrolling these circles fills a triangle with base 2 π r and height r (where r is the radius of the filled disk). Such a triangle has area π r². This does not serve as a complete proof for why this is the area of a circle, but can give you some intuition for why it should be. [code]

lostandfoundinprague:

Photographer of the month: Jiří Jeníček, Prague, Rooftops of Mala Strana, 40’s