Permalink Submitted by skothr on September 9, 2021

[I just realized my response had a random link, so it may have been filtered. This is a direct copy without the link.]

I agree with some of your points at a high level, but at the very least they do have the equation correct. It's not an approximation -- the irrationality is derived from the square root of 5. I was caught off guard myself when I first saw such a simply-defined expression being equated to phi.

But the math works out to the same expression you provided.

## equation

[I just realized my response had a random link, so it may have been filtered. This is a direct copy without the link.]

I agree with some of your points at a high level, but at the very least they do have the equation correct. It's not an approximation -- the irrationality is derived from the square root of 5. I was caught off guard myself when I first saw such a simply-defined expression being equated to phi.

But the math works out to the same expression you provided.

Let x = (1 + sqrt(5)) / 2

Prove:

x = 1 + 1 / x

Calculate 1/x:

1/x

= 1 / ((1 + sqrt(5)) / 2)

= 2 / (1 + sqrt(5)) : [1/(a/b) = b/a]

= 2*(1 - sqrt(5)) / (1 - 5) : [multiply by (1 - sqrt(5))/(1 - sqrt(5))]

= 2*(1 - sqrt(5)) / (-4) : [simplify denominator by addition]

= (1 - sqrt(5)) / (-2) : [cancel out factor of 2]

= (sqrt(5) - 1) / 2 : [bring negative sign up to the numerator]

That's 1/x, so now add 1 to get (1 + 1/x):

1+1/x

= 2/2 + (sqrt(5) - 1) / 2 : [2/2 = 1 and 1/x = (sqrt(5) - 1) / 2]

= (2 + sqrt(5) - 1) / 2 : [combine fractions with same denominator]

= (1 + sqrt(5)) / 2 : [combine terms in numerator, 2 - 1 = 1]

= x

Thus, x = 1 + 1/x if x = (1+sqrt(5))/2

ΟΕΔ

Personally, the significance of the square root of 5 reminds me of the dodecahedron (made of pentagons) which Plato thought to represent the cosmos.