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A332328
Decimal expansion of the least positive zero of the 8th Maclaurin polynomial of cos x.
0
1, 5, 7, 0, 8, 2, 1, 0, 6, 7, 9, 5, 3, 3, 9, 0, 7, 2, 9, 1, 7, 2, 8, 2, 1, 1, 5, 3, 1, 4, 9, 2, 4, 9, 5, 5, 3, 1, 6, 1, 6, 6, 5, 8, 4, 3, 6, 0, 0, 3, 5, 7, 8, 5, 6, 5, 3, 7, 7, 3, 2, 5, 2, 7, 2, 0, 4, 0, 5, 0, 3, 7, 0, 5, 0, 3, 8, 6, 3, 5, 8, 3, 0, 4, 4, 4
OFFSET
1,2
COMMENTS
The Maclaurin polynomial p(2n,x) of cos x is 1 - x^2/2! + x^4/4! + ... + (-1)^n x^(2n)/(2n)!.
Let z(n) be the least positive zero of p(2n,x). The limit of z(n) is Pi/2 = 1.570796326..., as in A019669.
EXAMPLE
Least positive zero = 1.5708210679533907291728211531492495531616658...
MATHEMATICA
z = 150; p[n_, x_] := Normal[Series[Cos[x], {x, 0, n}]]
t = x /. NSolve[p[8, x] == 0, x, z][[5]]
u = RealDigits[t][[1]]
Plot[Evaluate[p[8, x]], {x, -1, 2}]
CROSSREFS
Sequence in context: A085679 A019669 A088394 * A021950 A072417 A133412
KEYWORD
nonn,cons,easy
AUTHOR
Clark Kimberling, Feb 11 2020
STATUS
approved