

A235509


Decimal expansion of arccos(4/5).


1



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

0,1


COMMENTS

Given a square ABCD, there is one point M equidistant from A, B and the middle of CD. The measure of the angle BAM is arccos(4/5) (or arcsec(5/4)). This angle is the smallest angle of the wellknown (3, 4, 5) Pythagorean triangle.
Also the polar angle phi of the viewing cone that cuts out exactly 10% of the celestial sphere; phi = arccos(12f), where f is the cutout fraction of the full solid angle.  Stanislav Sykora, Feb 14 2016


LINKS

Table of n, a(n) for n=0..99.
JeanFrançois Alcover, Figure showing square ABCD and angle BAM


FORMULA

Cos(A235509) + cos(A195771) = 1.


EXAMPLE

0.64350110879328438680280922871732263804151059111531238286560611871351...
In degrees: 36.869897645844...°


MATHEMATICA

RealDigits[ArcCos[4/5], 10, 100] // First


CROSSREFS

Cf. A195771.
Sequence in context: A182618 A118227 A199429 * A224927 A200104 A154747
Adjacent sequences: A235506 A235507 A235508 * A235510 A235511 A235512


KEYWORD

nonn,cons


AUTHOR

JeanFrançois Alcover, Jan 14 2014


STATUS

approved



