Difference between revisions of "Phi"
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<math>\phi</math> appears in a variety of different mathematical contexts: it is the limit of the ratio of successive terms of the [[Fibonacci sequence]], as well as the positive solution of the [[quadratic equation]] <math>x^2-x-1=0</math>. | <math>\phi</math> appears in a variety of different mathematical contexts: it is the limit of the ratio of successive terms of the [[Fibonacci sequence]], as well as the positive solution of the [[quadratic equation]] <math>x^2-x-1=0</math>. | ||
| − | <math>\phi</math> is also equal to the | + | <math>\phi</math> is also equal to the continued fraction <math>1+\frac{1}{1+\frac{1}{1+\frac{1}{1+\frac{1}{1+\cdots}}}}</math> and the continued radical <math>\sqrt{1+\sqrt{1+\sqrt{1+\sqrt{1+\cdots}}}}</math>. It is the only positive real number that is one more than its multiplicative inverse. |
It is also <math>{\lim_{x \to \infty}} \frac{F_{x+1}}{F_x}</math> where <math>F_n</math> is the nth number in the [[Fibonacci sequence]]. | It is also <math>{\lim_{x \to \infty}} \frac{F_{x+1}}{F_x}</math> where <math>F_n</math> is the nth number in the [[Fibonacci sequence]]. | ||
==Golden ratio== | ==Golden ratio== | ||
| − | <math>\phi</math> is also known as the Golden Ratio. It was commonly believed by the Greeks to be the most aesthetically pleasing ratio between side lengths in a [[rectangle]]. The | + | <math>\phi</math> is also known as the Golden Ratio. It was commonly believed by the Greeks to be the most aesthetically pleasing ratio between side lengths in a [[rectangle]]. The Golden Rectangle is a rectangle with side lengths of 1 and <math>\phi</math>; it has a number of interesting properties. |
The first fifteen digits of <math>\phi</math> in decimal representation are <math>1.61803398874989</math> | The first fifteen digits of <math>\phi</math> in decimal representation are <math>1.61803398874989</math> | ||
Revision as of 18:53, 11 January 2013
Phi (in lowercase, either 
or 
; capitalized, 
) is the 21st letter in the Greek alphabet. It is used frequently in mathematical writing, often to represent the constant 
. (The Greek letter tau (
) was also used for this purpose in pre-Renaissance times.)
Contents
Use
appears in a variety of different mathematical contexts: it is the limit of the ratio of successive terms of the Fibonacci sequence, as well as the positive solution of the quadratic equation 
.
is also equal to the continued fraction 
and the continued radical 
. It is the only positive real number that is one more than its multiplicative inverse.
It is also 
where 
is the nth number in the Fibonacci sequence.
Golden ratio
is also known as the Golden Ratio. It was commonly believed by the Greeks to be the most aesthetically pleasing ratio between side lengths in a rectangle. The Golden Rectangle is a rectangle with side lengths of 1 and ; it has a number of interesting properties.
The first fifteen digits of in decimal representation are 
Other Usages
is also commonly used to represent Euler's totient function.
