MHB Uncovering Patterns in Questions

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The discussion focuses on identifying patterns in the remainders of powers of two when divided by seven, specifically noting that the remainder is influenced by the exponent's division by three. Participants suggest analyzing the remainders of triangular numbers, represented as k(k+1)/2, when divided by three to uncover further patterns. The conversation emphasizes the importance of modular arithmetic in understanding these relationships. Ultimately, the goal is to establish a clear pattern that can be applied to similar mathematical problems. Understanding these patterns can enhance problem-solving skills in number theory.
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Please help me to find pattern in this question
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Hi SumitKumar, and welcome to MHB!

The remainder when $2^n$ is divided by $7$ depends on the remainder when the exponent $n$ is divided by $3$. So you need to work out the pattern of remainders when numbers of the form $\dfrac{k(k+1)}2$ are divided by $3$.
 
Seemingly by some mathematical coincidence, a hexagon of sides 2,2,7,7, 11, and 11 can be inscribed in a circle of radius 7. The other day I saw a math problem on line, which they said came from a Polish Olympiad, where you compute the length x of the 3rd side which is the same as the radius, so that the sides of length 2,x, and 11 are inscribed on the arc of a semi-circle. The law of cosines applied twice gives the answer for x of exactly 7, but the arithmetic is so complex that the...