definition
Chris Impens defines the number (phi) as the positve number to which the condition applies: .
He adds that it's not necessary to define as a ratio of sides or parts of a segment.
In Pythagorean time geometry and algebra weren't distinct disciplines. Numbers too were depicted graphically.
While learning about fractions we also work with parts of chocolate or pizza's, but don't always continue illustrating starting from the construction of the perpendicular bisector of a segment.
The definition results in the number 0.618...
Note
The reverse of is represented with the symbol (= capital letter Phi).
As a value you find
You can control that the definition is correct for the expression found:
