Silver ratio

In mathematics, the silver ratio is a geometrical proportion with exact value 1 + √2, the positive solution of the equation x = 2x + 1.

The name silver ratio is by analogy with the golden ratio, the positive solution of the equation x = x + 1.

Although its name is recent, the silver ratio (or silver mean) has been studied since ancient times because of its connections to the square root of 2, almost-isosceles Pythagorean triples, square triangular numbers, Pell numbers, the octagon, and six polyhedra with octahedral symmetry.