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Decimal expansion of greatest x satisfying x^2 - cos(x) = 4*sin(x).
3

%I #8 Jun 24 2018 14:49:19

%S 1,8,7,5,2,0,0,6,8,8,7,5,6,6,9,0,1,3,7,0,0,0,9,9,5,4,4,2,7,0,2,2,4,9,

%T 1,3,9,1,5,1,8,7,1,7,6,0,4,2,4,5,7,9,4,7,0,6,9,5,5,6,0,1,4,9,5,6,5,1,

%U 5,3,3,6,8,6,6,1,5,7,7,6,9,0,2,9,6,4,3,2,2,4,4,2,9,3,0,2,1,2,4

%N Decimal expansion of greatest x satisfying x^2 - cos(x) = 4*sin(x).

%C See A199949 for a guide to related sequences. The Mathematica program includes a graph.

%H G. C. Greubel, <a href="/A200017/b200017.txt">Table of n, a(n) for n = 1..10000</a>

%e least x: -0.231931736508077068279216295078080...

%e greatest x: 1.87520068875669013700099544270224...

%t a = 1; b = -1; c = 4;

%t f[x_] := a*x^2 + b*Cos[x]; g[x_] := c*Sin[x]

%t Plot[{f[x], g[x]}, {x, -1, 2}, {AxesOrigin -> {0, 0}}]

%t r = x /. FindRoot[f[x] == g[x], {x, -.24, -.23}, WorkingPrecision -> 110]

%t RealDigits[r] (* A200016 *)

%t r = x /. FindRoot[f[x] == g[x], {x, 1.87, 1.88}, WorkingPrecision -> 110]

%t RealDigits[r] (* A200017 *)

%o (PARI) a=1; b=-1; c=4; solve(x=1, 2, a*x^2 + b*cos(x) - c*sin(x)) \\ _G. C. Greubel_, Jun 24 2018

%Y Cf. A199949.

%K nonn,cons

%O 1,2

%A _Clark Kimberling_, Nov 12 2011