The Kepler triangle is a right triangle whose sides are in a geometric progression. If the sides are formed from the geometric progression a, ar, ar2 then its common ratio r is given by r = √φ where φ is the golden ratio. Its sides are therefore in the ratio 
Phi( φ) is calculated as a/b where a and b are the non hypotenuse sides of the triangle
φ = a+b/a = a/b