3²/4²/5²

The "3-4-5 right triangle" is one of the most famous triangles: it's the classic example of the Pythagorean theorem, which states that the sum of the squares of the lengths of the two legs of a right triangle is equal to the square of the length of the hypotenuse. Today's date—if you'll allow the "American" format—is 3²/4²/5², so let us celebrate before this bastion of mathematics.

The Pythagorean theorem states that for any right triangle, a² + b² = c².