help with equation in function component - catenary from two points - where is arcsinh function?

by Manuel

Aug 28, 2009

I want to calculate these equation in a function component:
sinh^(-1)[h/sqrt(s^2 - h^2)] - L/(2a) but it's not working...
Can someone help me with the correct syntax for the "expression editor" in grasshopper?

PD: "h", "L" and "a" are inputs variables.


I'm trying to do a catenary from two points like in these video: http://www.grasshopper3d.com/video/catenaria-1


The equation it's suppose to be the "A" constant in the catenary equation: y(x) = a cosh(x/a + A) + B
The "B" constant is B = -a cosh A
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  • up

    Vicente Soler

    Wikipedia says it's "y = a*cosh(x/a)"
    I just tried it and it works fine. At least it looks just like the graph:
    http://en.wikipedia.org/wiki/Catenary#Mathematical_description

    Aug 29, 2009

    • up

      Giulio Piacentino

      Hi Manuel, here are some inverses of hyperbolic functions:

      Inverse Hyperbolic Sine: ArcSinH(X) = Math.Log(X + Math.Sqrt(X * X + 1));
      Inverse Hyperbolic Cosine: ArcCosH(X) = Math.Log(X + Math.Sqrt(X * X - 1));
      Inverse Hyperbolic Tangent: ArcTanH(X) = Math.Log((1 + X) / (1 - X)) * 0.5;

      I remember the list being on the VBScript help, which can also be found here.

      A sample in VB.net and C# scripts that should help you in your task is attached.
      25

      Aug 30, 2009

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      • up

        Bojan Koncarevic

        Dear David

        I have a problem with the catenary gh component..

        It does outcomes in a curve as You have attached the set of curves creating the arched tunnel..

        but actually it gives out the simple triangle connection of the 2 base point and height ending point

        What i am doing wrong (since i do not have curve (actualy i do but it is not the curved one) ; ) )

        I hope i will get the reply asap your schedule can estimate..

        I did not upload any file since the question is very simple.

        I just simply make 2 points and catch them to the Catenary icon (or line end points)

         

        best

        Bojan

        Nov 30, 2011