HOW TO FIND PYTHAGOREAN TRIPLET FROM ONE NUMBER

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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