S = {a, b, c}
Here a, b , c are Pythagorean triplets.
Let us first take the smallest triplet 3,4,5
Now as 3 is a prime number, GCD shall be 1
Another one is 5, 12 , 13.
Here 13 is a prime number, so GCD shall be 1
Next one is 20,21, 29
Here 29 is a prime number, so GCD = 1
For 15, 8, 17
17 is a prime number so GCD = 1
Now when none of them is a prime number'
For 77,36, 85
77 = 7 ×11
36 = 2 × 2 ×3 ×3
85 = 5 × 17
Here also the GCD is 1
So For S = {a, b, c} the Pythagorean triplets the GCD is always 1.