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A131503
Nonnegative integers n for which cos(n) is positive.
10
0, 1, 5, 6, 7, 11, 12, 13, 14, 18, 19, 20, 24, 25, 26, 30, 31, 32, 37, 38, 39, 43, 44, 45, 49, 50, 51, 55, 56, 57, 58, 62, 63, 64, 68, 69, 70, 74, 75, 76, 81, 82, 83, 87, 88, 89, 93, 94, 95, 99, 100, 101, 102, 106, 107, 108, 112, 113, 114, 118, 119, 120, 125, 126, 127, 131, 132
OFFSET
1,3
Nonnegative integers n satisfying sin(n)<sec(n). - Clark Kimberling, Aug 26 2014
This is proved by taking sec(n)=1/cos(n), therefore considering sin(n)*cos(n)<1 for cos(n)>0 and sin(n)*cos(n)>1 for cos(n)<0. Since sin(n)*cos(n)=sin(2n)/2, the first case becomes sin(2n)<2 for cos(n)>0 which is always correct, and the second case becomes sin(2n)>2 for cos(n)<0 which is never correct. - R. J. Mathar, Sep 07 2014
Eric Weisstein's World of Mathematics, Cosine
MATHEMATICA
Select[Range[150], Cos[#]>0&] (* Harvey P. Dale, Feb 02 2012 *)
PROG
(Sage) [i for i in range(200) if cos(i)>0] # Danny Rorabaugh, Mar 19 2015
(PARI) lista(nn) = for (n=0, nn, if (cos(n) > 0, print1(n, ", "))); \\ Michel Marcus, Mar 19 2015
CROSSREFS
Sequence in context: A104122 A336857 A049467 * A047266 A026309 A073936
KEYWORD
easy,nonn
AUTHOR
Stephen Casey (hexomino(AT)gmail.com), Aug 13 2007
EXTENSIONS
0 inserted by R. J. Mathar, Sep 06 2014
STATUS
approved

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Last modified September 20 06:43 EDT 2024. Contains 376067 sequences. (Running on oeis4.)