OFFSET
1,2
COMMENTS
Angle in radians of the obtuse angle of the obtuse scalene triangle with sides of lengths 2, 3 and 4, the scalene triangle with least integer side lengths.
Arccos(-1/4) is the least positive x for which the function f(x)=cos(x)+cos(2x) attains its minimum value, which is -9/8. - Clark Kimberling, Oct 28 2011
FORMULA
arccos(-1/4) = Pi - arcsin(sqrt(15)/4) = Pi - arctan(sqrt(15)).
EXAMPLE
1.82347658193697527271697912863346241435077843278439110412139607489448326362...
MATHEMATICA
RealDigits[ArcCos[-1/4], 10, 120][[1]] (* Harvey P. Dale, Dec 20 2016 *)
PROG
(PARI) acos(-1/4)
CROSSREFS
KEYWORD
cons,nonn
AUTHOR
Rick L. Shepherd, May 14 2008
STATUS
approved