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A178817
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Decimal expansion of the area of the regular 7-gon (heptagon) of edge length 1.
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10
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3, 6, 3, 3, 9, 1, 2, 4, 4, 4, 0, 0, 1, 5, 8, 8, 9, 9, 2, 5, 3, 6, 1, 9, 3, 0, 0, 7, 6, 0, 0, 2, 2, 0, 5, 7, 8, 7, 3, 5, 0, 1, 0, 3, 6, 1, 5, 9, 5, 4, 4, 4, 9, 1, 7, 1, 4, 5, 9, 8, 0, 4, 0, 9, 5, 1, 0, 2, 9, 9, 8, 5, 2, 3, 6, 3, 0, 4, 6, 0, 0, 5, 5, 6, 2, 7, 3, 0, 7, 1, 5, 2, 9, 5, 8, 1, 0, 8, 9, 4, 3, 7, 1, 0, 4
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OFFSET
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1,1
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LINKS
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FORMULA
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Equals (7/4) * cot(Pi/7).
Equals 7 / (4 * tan(Pi/7)) = 7 / (4 * A343058).
Equals sqrt(7/3 * (35 + 2 * 196^(1/3) * ((13 - 3 * sqrt(3) * i)^(1/3) + (13 + 3 * sqrt(3) * i)^(1/3)))) / 4.
Equals sqrt(7/4) * sqrt(35/12 + (637/54 - sqrt(-2401/108))^(1/3) + (637/54 + sqrt(-2401/108))^(1/3)).
(End)
A root of the polynomial 4096*x^6 - 62720*x^4 + 115248*x^2 - 16807. - Joerg Arndt, Jan 02 2023
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EXAMPLE
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3.63391244400158899253619300760022057873501036159544491714598040951029...
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MAPLE
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MATHEMATICA
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RealDigits[7*Cot[Pi/7]/4, 10, 100][[1]]
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PROG
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(PARI) p=7; a=(p/4)*cotan(Pi/p) \\ Set realprecision in excess. - Stanislav Sykora, Apr 12 2015
(Magma) SetDefaultRealField(RealField(100)); R:=RealField(); 7*Cot(Pi(R)/7)/4; // G. C. Greubel, Jan 22 2019
(Sage) numerical_approx(7*cot(pi/7)/4, digits=100) # G. C. Greubel, Jan 22 2019
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CROSSREFS
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KEYWORD
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AUTHOR
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STATUS
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approved
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