Thursday, April 16, 2009


PYTHAGOREAN TRIPLE

It is surprising that there are some right-angled triangles where all three sides are whole numbers. The three whole number side-lengths are called a Pythagorean triple.

An example is a = 3, b = 4 and c = 5, called "the 3-4-5 triangle". 32+42 = 9 + 16 = 25 = 52 so a2 + b2 = c2.

Notice that the greatest common divisor of the three numbers 3, 4, and 5 is 1.

Pythagorean triples with this property are called primitive. From primitive Pythagorean triples, you can get other, imprimitive ones, by multiplying each of a, b, and c by any positive whole number d > 1. This is because

a2 + b2 = c2 if and only if (da)2 + (db)2 = (dc)2.

Thus (a,b,c) is a Pythagorean triple if and only examples if (da,db,dc) is. For example, (6,8,10) and (9,12,15) are imprimitive Pythagorean triples.

Here are the of the first few primitive Pythagorean triples

a

b

c


a

b

c


a

b

c


3

4

5

5

12

13

7

24

25

8

15

17

9

40

41

11

60

61

12

35

37

13

84

85

16

63

65

36

77

85

39

80

89

48

55

73

CHALLENGE YOURSELF

1. Find the only Pythagorean triangles with an area equal to their perimeter.

2. Ahmad has a triangular orchard with sides measuring 560 m, 420 m and 300 m. Determine whether the shape of his orchard is a right-angled, obtuse-angled or acute-angled triangle.