Consider the following,
32 + 42 = 52
The collection of numbers 3, 4 and 5 is known as Pythagorean triplet.
Relationship between Pythagorean Triplet :
Square of larger number
= Sum of squares of other two small numbers
If the given numbers will have the above relationship, we can say the given numbers are pythagorean triplets.
For any natural number m > 1, we have
(2m)2 + (m2 - 1)2 = (m2 + 1)2
So, 2m, (m2 - 1) and (m2 + 1) forms a Pythagorean triplet.
Example 1 :
Find the Pythagorean triplet in which one number is 8.
Solution :
We can get the Pythagorean triplet by using the general form 2m, (m2 - 1), (m2 + 1).
Let us consider the given number as 2m
2m = 8
m = 4
(m2 - 1) = (42 - 1) = 16 - 1 = 15 |
(m2 + 1) = (42 + 1) = 16 + 1 = 17 |
The triplet is 8, 15 and 17.
Verifying the relationship :
172 = 152 + 82
289 = 225 + 64
289 = 289
Example 2 :
Find the Pythagorean triplet in which one number is 12.
Solution :
We can get the Pythagorean triplet by using the general form 2m, (m2 - 1), (m2 + 1).
Let us consider the given number as 2m
2m = 12
m = 6
(m2 - 1) = (62 - 1) = 36 - 1 = 35 |
(m2 + 1) = (62 + 1) = 36 + 1 = 37 |
The triplet is 12, 35 and 37.
Verifying the relationship :
372 = 352 + 122
1369 = 1225 + 144
1369 = 1369
Example 3 :
Find the Pythagorean triplet in which one number is 14.
Solution :
We can get the Pythagorean triplet by using the general form 2m, (m2 - 1), (m2 + 1).
Let us consider the given number as 2m
2m = 14
m = 7
(m2 - 1) = (72 - 1) = 49 - 1 = 48 |
(m2 + 1) = (72 + 1) = 49 + 1 = 50 |
The triplet is 14, 48 and 50.
Verifying the relationship :
502 = 482 + 142
2500 = 2304 + 196
2500 = 2500
Example 4 :
Find the Pythagorean triplet in which one number is 6.
Solution :
We can get the Pythagorean triplet by using the general form 2m, (m2 - 1), (m2 + 1).
Let us consider the given number as 2m
2m = 6
m = 3
(m2 - 1) = (32 - 1) = 9 - 1 = 8 |
(m2 + 1) = (32 + 1) = 9 + 1 = 10 |
The triplet is 6, 8 and 10.
Verifying the relationship :
102 = 82 + 62
100 = 64 + 36
100 = 100
Example 5 :
Find the Pythagorean triplet in which one number is 16.
Solution :
We can get the Pythagorean triplet by using the general form 2m, (m2 - 1), (m2 + 1).
Let us consider the given number as 2m
2m = 16
m = 8
(m2 - 1) = (82 - 1) = 64 - 1 = 63 |
(m2 + 1) = (82 + 1) = 64 + 1 = 65 |
The triplet is 16, 63 and 65.
Verifying the relationship :
652 = 632 + 162
4225 = 3969 + 256
4225 = 4225
Example 5 :
Suppose m and n are two numbers. If m2 - n2, 2mn and m2 + n2 are the three sides of a triangle, then show that it is a right triangle and hence write any two pairs of Pythagorean triplet.
Solution :
The sides of the right triangle are m2 - n2, 2mn and m2 + n2
(m2 - n2)2 + (2mn)2 = (m2 + n2)2
L.H.S :
= (m2 - n2)2 + (2mn)2
= (m2)2 - 2m2 n2 + (n2)2 + 4m2 n2
= (m2)2 + 2m2 n2 + (n2)2
= (m2 + n2)2
R.H.S
So, the given measures are sides of the right triangle.
Example 6 :
In a right angled triangle if one side forming the right angle is 6 and the hypotenuse is 10. What is the length of the other right angle forming side?
a) 8 b) 10 c) 12 d) 6
Solution :
The longest side of a right triangle = hypotenuse
Let the other side be x.
The other two sides are 6 and x.
Square of hypotenuse = sum of squares of remaining two sides
102 = 62 + x2
100 = 36 + x2
x2 = 100 - 36
x2 = 64
x = 8
So, the other side of the right triangle = 8 cm.
Option a is correct.
Example 6 :
Pythagoras theorem can only be applied on ________ triangles.
a) equilateral b) isosceles c) right angled
d) isosceles right angled
Solution :
Pythagoras theorem can only be applied on right angled triangles.
Example 7 :
3, 4 & 5 are not a Pythagorean triplet.
a) True b) False
Solution :
Let a = 3, b = 4 and c = 5
c2 = a2 + b2
52 = 32 + 42
25 = 9 + 16
25 = 25
So, the given measures are Pythagorean triples. It is true.
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