

A197688


Decimal expansion of 2*Pi/(4+Pi).


2



8, 7, 9, 8, 0, 1, 6, 9, 2, 9, 7, 6, 8, 8, 5, 2, 4, 8, 1, 7, 9, 0, 4, 2, 7, 4, 9, 0, 2, 7, 4, 2, 6, 7, 6, 7, 5, 9, 8, 3, 7, 4, 8, 8, 6, 4, 7, 5, 3, 7, 8, 4, 8, 2, 5, 3, 1, 8, 9, 9, 7, 3, 6, 2, 5, 1, 6, 8, 0, 4, 2, 6, 1, 6, 7, 8, 0, 6, 1, 9, 5, 3, 7, 3, 7, 0, 0, 9, 1, 5, 8, 7, 3, 8, 5, 2, 6, 7, 0
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OFFSET

0,1


COMMENTS

Least x>0 such that sin(bx)=cos(cx) (and also sin(cx)=cos(bx)), where b=1 and c=pi/4; see the Mathematica program for a graph and A197682 for a discussion and guide to related sequences.
This number is the pressure drag coefficient for Kirchhoff flow past a plate, calculated by Kirchhoff (1969) for an infinitely long plate; see References.  Peter J. C. Moses and Clark Kimberling, Sep 07 2013


REFERENCES

Herbert Oertel and P. Erhard, PrandtlEssentials of Fluid Mechanics, Springer, 2010, pages 163164.


LINKS

Table of n, a(n) for n=0..98.


EXAMPLE

x=0.8798016929768852481790427490274267675983748864...


MATHEMATICA

b = 1; c = Pi/4;
t = x /. FindRoot[Sin[b*x] == Cos[c*x], {x, .8, .9}]
N[Pi/(2*b + 2*c), 110]
RealDigits[%] (* A197688 *)
Simplify[Pi/(2*b + 2*c)]
Plot[{Sin[b*x], Cos[c*x]}, {x, 0, Pi/2}]


PROG

(PARI) 2*Pi/(4+Pi) \\ Charles R Greathouse IV, Jul 22 2014


CROSSREFS

Cf. A197682.
Sequence in context: A021536 A199389 A256490 * A094082 A318378 A198884
Adjacent sequences: A197685 A197686 A197687 * A197689 A197690 A197691


KEYWORD

nonn,cons


AUTHOR

Clark Kimberling, Oct 17 2011


STATUS

approved



