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%I #44 Aug 21 2023 12:39:05
%S 6,9,0,9,8,3,0,0,5,6,2,5,0,5,2,5,7,5,8,9,7,7,0,6,5,8,2,8,1,7,1,8,0,9,
%T 4,1,1,3,9,8,4,5,4,1,0,0,9,7,1,1,8,5,6,8,9,3,2,2,7,5,6,8,8,6,4,7,3,6,
%U 9,7,6,8,5,9,0,5,4,8,7,7,5,1,4,6,3,9,6,3,9,7,9,0,5,3,0,4,4,3,1,2,5,7,6,2,2
%N Decimal expansion of (3-phi)/2, where phi is the golden ratio.
%C This is the height h of the isosceles triangle in a regular pentagon inscribed in the unit circle formed from a diagonal as base and two adjacent pentagon sides. h = sqrt(sqrt(3-phi)^2 - (sqrt(2 + phi)/2)^2) = sqrt(10 - 5*phi)/2 = (3 - phi)/2. - _Wolfdieter Lang_, Jan 07 2018
%H Ivan Panchenko, <a href="/A187798/b187798.txt">Table of n, a(n) for n = 0..1000</a>
%H <a href="/index/Al#algebraic_02">Index entries for algebraic numbers, degree 2</a>
%F Equals (3-phi)/2 = A094874/2 with phi from A001622.
%e 0.6909830056250525758977065828171809411398454100971185689322756886473697685905...
%t RealDigits[(3 - GoldenRatio)/2, 10, 111][[1]] (* or *)
%t RealDigits[(5 - Sqrt[5])/4, 10, 111][[1]] (* _Robert G. Wilson v_, Jan 07 2018 *)
%o (PARI) (5-sqrt(5))/4 \\ _Charles R Greathouse IV_, Aug 31 2013
%Y Cf. A001622, A187426, A226765, A094874.
%K nonn,cons
%O 0,1
%A _Joost Gielen_, Aug 30 2013
%E Extended by _Charles R Greathouse IV_, Aug 31 2013
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