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Part of 1998 Baltic Way

Problems(1)

c is divisible by 5 in quasi-pythagorean triplet

Source: Baltic Way 1998

1/11/2011
A triple (a,b,c)(a,b,c) of positive integers is called quasi-Pythagorean if there exists a triangle with lengths of the sides a,b,ca,b,c and the angle opposite to the side cc equal to 120āˆ˜120^{\circ}. Prove that if (a,b,c)(a,b,c) is a quasi-Pythagorean triple then cc has a prime divisor bigger than 55.
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