A197139 Decimal expansion of the shortest distance from the x axis through (3,2) to the line y = x.

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

Offset: 1

Author

Clark Kimberling, Oct 10 2011

Keywords

• nonn
• cons

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.

Any Philo line can be constructed using the intersections of circles and hyperbolas. In this case, the Philo line passes though the two points at which the circle (x - 3/2)^2 + (y - 1)^2 = 13/4 and the hyperbola x*y - y^2 = 2 intersect. The circle has segment OP as diameter, where O(0,0) is the origin and P is the point (3,2). The asymptotes of the hyperbola are the x axis and the line y = x. Point P is one of the two points at which the circle and the hyperbola intersect. - Raul Prisacariu, Apr 06 2024

Examples

			Length of Philo line:   2.8861171058980012915367...
Endpoint on x axis:     (3.4883, 0); see A197138
Endpoint on line y = x: (2.80376, 2.80376)
		

Crossrefs

Cf. A197032, A197138, A197008, A195284.

Programs

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 = 1; h = 3; k = 2;(* slope m; point (h,k) *)
t = t1 /. FindRoot[p[t1] == 0, {t1, 1, 2}, WorkingPrecision -> 100]
RealDigits[t]  (* A197138 *)
{N[t], 0} (* endpoint on x axis *)
{N[k*t/(k + m*t - m*h)],
N[m*k*t/(k + m*t - m*h)]} (* endpoint on line y=x *)
d = N[Sqrt[f[t]], 100]
RealDigits[d]  (* this sequence *)
Show[Plot[{k*(x - t)/(h - t), m*x}, {x, 0, 4}],
ContourPlot[(x - h)^2 + (y - k)^2 == .003, {x, 0, 4}, {y, 0, 3}],
PlotRange -> {0, 3}, AspectRatio -> Automatic]

Extensions

Last digit removed (repr. truncated, not rounded up) by R. J. Mathar, Nov 08 2022