# Math Is Fun Forum

Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫  π  -¹ ² ³ °

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## #1 2009-11-17 10:15:19

EinsteinJr10
Member
Registered: 2009-11-08
Posts: 1

### The Golden Ratio

Knowing that ϕ²=ϕ−1, find ϕ-²

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## #2 2009-11-17 12:18:36

mathsyperson
Moderator
Registered: 2005-06-22
Posts: 4,900

### Re: The Golden Ratio

ϕ[sup]2[/sup] = ϕ - 1

ϕ = 1 - ϕ[sup]-1[/sup]

ϕ[sup]-1[/sup] = 1 - ϕ

ϕ[sup]-2[/sup] = (1-ϕ)[sup]2[/sup]

ϕ[sup]-2[/sup] = 1 - 2ϕ + ϕ[sup]2[/sup]

ϕ[sup]-2[/sup] = 1 - 2ϕ + (ϕ - 1)

ϕ[sup]-2[/sup] = -ϕ

This may seem counterintuitive, but it's worth noting that ϕ must be a complex number.

Why did the vector cross the road?
It wanted to be normal.

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## #3 2009-11-22 17:34:57

scientia
Member
Registered: 2009-11-13
Posts: 224

### Re: The Golden Ratio

If ϕ is the golden ratio, ϕ² should be ϕ+1, not ϕ−1.

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## #4 2010-08-16 16:33:09

jonnyj99
Member
Registered: 2010-08-16
Posts: 4

### Re: The Golden Ratio

In mathematics and the arts, both quantities are in the golden ratio if the ratio between the total amounts to the largest number is equal to (=) the ratio of highest to lowest amount of Euclid one.Although not use the term, we call Build this golden ratio.First an isosceles triangle whose base angles are twice the angle at the top.

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