PYTHAGORAS THEOREM AND FIBONACCI NUMBERS

     

Pythagoras was born on the island of Samos, Greece, in 569 BC.He excelled as a student and, as a young man, he traveled widely . Tradition says that he explored from India in the East to Gaul in the West.Pythagoras traveled extensively through Egypt, learning maths, astronomy and music. Pythagoras left Samos in disgust for its ruler Polycrates. He moved on to the Greek city of Crotona, located on the southern shore of Italy. There he created a school where his followers lived and worked.It was a mystical learning community.

At the heart of Pythagoras` teachings was the vision of the underlying harmony of the universe. This harmony had to be abstracted from the confusion of visible things and daily events. As a matter of fact this harmony existed in the abstract - in the same way as numbers and mathematical formulas are abstractions.
Pythagoras believed in secrecy and communalism, so it is almost impossible distguishing his work from the work of his followers. Pythagoras and his followers contributed to music, astronomy and mathematics. He died about 500 BC in Metapontum, Lucania.

Pythagoras` desire was to find the mathematical harmonies of all things. The study of of odd, even, prime and square numbers were among numerous mathematical investigations of the Pythagoreans. This helped them develop a basic understanding of mathematics and geometry to build their Pythagorean theorem.
The Pythagorean Theorem states that the square of the hipotenyse of a right triangle is equal to the sum of the squares of the other two sides.

Pythagoras Theorem asserts that for a right triangle with the short sides of the length a and b and the long side of the length c
a2 + b2 = c2

A Pythagorean Triangle is a right angled triangle which sides are whole numbers. There is an easy way to generate Pythagorean triangles using 4 Fibonacci numbers. Take, for example, the 4 Fibonacci numbers 1,2,3 and 5 .
We can now make a Pythagorean Triangle as follows :

     

Mutiply the two middle or inner numbers
here 2 and 3 giving 6;
Double the results
here twice 6 gives 12
That is one side, a, of the Pythagorean Triangle:
a=2*F(n+1)*F(n+2)
Multiply together the two outer numbers
here 1 and 5 giving 5.
This is the second side, b, of the Pythagorean Triangle:
b=F(n)*F(n+3)
The third side, the longest one, is found by adding together the squares of the inner
two numbers
here 22=4 and 32=9 and their sum is 4+9=13.
This is the third side, c, of the Pythagorean Triangle:
c=F2(n+1) + F2(n+2)

     

We have generated 12, 5, 13 Pythagorean Triangle.

     

n
F(n)
F(n+1)
F(n+2)
F(n+3)
a
b
c
1
1
1
2
3
4
3
5
2
1
2
3
5
12
5
13
3
2
3
5
8
30
16
34
4
3
5
8
13
80
39
89
6
8
13
21
34
546
272
610
7
13
21
34
55
1428
715
1597
8
21
34
55
89
3740
1869
4181
9
34
55
89
144
9790
4869
10946

     

In fact, this process works not only for Fibonacci numbers but for Lucas numbers as well.

     

n
L(n)
L(n+1)
L(n+2)
L(n+3)
a
b
c
1
1
3
4
7
24
7
25
2
3
4
7
11
56
33
65
3
4
7
11
18
154
72
170
4
7
11
18
29
396
203
445
5
11
18
29
47
1044
517
1165
6
18
29
47
76
2726
1368
3050
7
29
47
76
123
7144
3567
7985
8
47
76
123
199
18696
9353
20905
9
76
123
199
322
48954
24472
54730

     

However, for a Pythagorean Triangle, we also want the sides to be Fibonacci numbers too.
It is triangle with sides
a=F(n), b=F(n+1) and c=sqrt(F(2n+1));
Here is a list of some Pythagorean triangles with sides which are Fibonacci numbers :

     

n
F2(n)
F2(n+1)
F(2*n+1)
1
1
1
2
2
1
4
5
3
4
9
13
4
9
25
34
5
25
64
89
6
64
169
175
7
169
441
610
8
441
1156
1597
9
1156
3025
4181

     

where

     

F2(n) + F2(n+1) = F(2*n+1)

     

Also, a Pythagorean Triangle can be a right angled triangle with sides which are Lucas numbers:
a=L(n), b=L(n+1) and c= sqrt( 5*L(2n+1))
Here is a list of some Pythagorean triangles with sides which are Lucas numbers:

     

n
L2(n)
L2(n+1)
5*F(2*n+1)
1
1
9
10
2
9
16
25
3
16
49
65
4
49
121
170
5
121
324
445
6
324
841
1165
7
841
2209
3050
8
2209
5776
7985
9
5776
15129
7305

     

where

     

L2(n) + L2(n+1) = 5*F(2*n+1)

     

or

     

     

By adding the square of Fibonacci ( or Lucas ) numbers we obtain many interesting relations:

     

F2(n) + 2*F2(n+1) + F2(n+2)= L(2*n+2)

L2(n) + 2*L2(n+1) + L2(n+2) = 5*L(2*n+2)

     

and

     

F2(n) + 3*F2(n+1) + 3*F2(n+2) + F2(n+3) = 5*F(2*n+3)

L2(n) + 3*L2(n+1) + 3*L2(n+2) + L2(n+3)= 25*F(2*n+3)

     

and

     

F2(n)+4F2(n+1)+6F2(n+2)+4F2(n+3)+F2(n+4)=5L(2n+4)

L2(n)+4L2(n+1)+6L2(n+2)+4L2(n+3)+L2(n+4)=25L(2n+4)

     

and

     

F2(n)+5F2(n+1)+10F2(n+2)+10F2(n+3)+5F2(n+4)+F2(n+5)=25F(2n+5)

L2(n)+5L2(n+1)+10L2(n+2)+10L2(n+3)+5L2(n+4)+L2(n+5)=125F(2n+5)

     

and so on...

     

     

or

     

     

In general case we have the next relation between Lucas and Fibonacci numbers:

     



See Also:  Fibonacci Numbers in Nature  Fibonacci Numbers and the Pascal Triangle   FIBONACCI IDENTITIES FROM MATRICES AND VECTORS    Fibonacci Numbers and The Natural Logarithmic Base, e   Archimedes` constant PI and the Fibonacci Numbers

     

     

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 © 2001-2005 Radoslav Jovanovic   translated by Dragutin Filipovic    created:  October 2002.