The Sacred Cut
 
Where the diagonal in the square cuts the elongated base line is the so-called sacred cut. This is the basis of the silver rectangle, and the A-format, it is also the point that indicates the doubling of the square. The diagonal in a square has the lenght of 1: �2 , which means that it is the root of a square which is the original square times two. This is the anciant way to double the square.
   
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