A197147 Decimal expansion of the shortest distance from the x axis through (4,1) to the line y=2x.

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

Offset

1,1

Comments

The shortest segment from one side of an angle T through a point P inside T is called the Philo line of P in T. For discussions and guides to related sequences, see A197032, A197008 and A195284.

Links

Table of n, a(n) for n=1..99.

Example

length of Philo line:    4.708000017496..
endpoint on x axis:    (4.92546, 0); see A197146
endpoint on line y=2x: (1.72768, 3.45536)

Mathematica

f[t_] := (t - k*t/(k + m*t - m*h))^2 + (m*k*t/(k + m*t - m*h))^2;
g[t_] := D[f[t], t]; Factor[g[t]]
p[t_] :=  h^2 k + k^3 - h^3 m - h k^2 m - 3 h k t + 3 h^2 m t + 2 k t^2 - 3 h m t^2 + m t^3
m = 2; h = 4; k = 1;  (* slope m, point (h, k) *)
t = t1 /. FindRoot[p[t1] == 0, {t1, 1, 2}, WorkingPrecision -> 100]
RealDigits[t]   (* A197146 *)
{N[t], 0}   (* endpoint on x axis *)
{N[k*t/(k + m*t - m*h)],
N[m*k*t/(k + m*t - m*h)]} (* endpt on line y=2x *)
d = N[Sqrt[f[t]], 100]
RealDigits[d]   (* A197147 *)
Show[Plot[{k*(x - t)/(h - t), m*x}, {x, 0, 5}],
ContourPlot[(x - h)^2 + (y - k)^2 == .004, {x, 0, 5}, {y, 0, 3}], PlotRange -> {0, 4}, AspectRatio -> Automatic]

Crossrefs

Cf. A197032, A197146, A197008, A195284.

Sequence in context: A200388 A200508 A020833 * A153117 A338926 A322166

Adjacent sequences: A197144 A197145 A197146 * A197148 A197149 A197150

Keyword

nonn,cons

Author

Clark Kimberling, Oct 11 2011

Status

approved