Topic: Best way to plot Hyperbolic Cosine curve

[David Hall]

OK, so Autocad wont draw one of these out of the box that I know of, so any idea how I should proceed?  All ideas welcome

[SDETERS]

What is the x and y formula and or function to plot the points to?

[David Hall]

cosh(x)=1/2(e^x + e^-x)
taken from here

[SDETERS]

Looked in me notes

I can not find anything where I have done this before. 

I have all kinds of different splines I can make but this is not one of them

Sorry

[Swift]

Hey Duh
Long time, No see
It's been a long day but see if this is in the neighborhood of being right

Code: [Select]

Option Explicit

Public Sub CMDRDUH()

Dim pl As AcadLWPolyline
Dim lowbound As Double
Dim upbound As Double
Dim step As Double
Dim e As Double
Dim pi As Double
Dim i As Double
Dim k As Integer
Dim coords() As Double
Dim start As Integer
Dim finish As Integer

start = 0
e = 2.7182818284
pi = 3.14159265

lowbound = 0
upbound = pi * 2

step = 0.01

finish = (upbound - lowbound) / step
ReDim coords(finish * 2 + 1)
i = 0: k = 0

For i = lowbound To upbound Step step

    coords(k) = i
    k = k + 1
    coords(k) = 0.5 * (e ^ i + e ^ -1)
    'coords(k) = Sin(i)
    k = k + 1
Next i

Set pl = ThisDrawing.ModelSpace.AddLightWeightPolyline(coords)

End Sub


[Bryco]

Looks good Swift
Can this be expressed as a spline?

[Swift]

That can be used to graph any function valid in two dimensions

[David Hall]

Cool, I will give that a try!  Thanks Swift

[David Hall]

    coords(k) = 0.5 * (e ^ i + e ^ -1)

Hey Swift, should this be 0.5*(e^i+e^-i) or -1?

[David Hall]

It looks like it draws the curve either way though, so Im confused

[Swift]

    coords(k) = 0.5 * (e ^ i + e ^ -1)

Hey Swift, should this be 0.5*(e^i+e^-i) or -1?

Your right...Sorry about that. The reason its not real noticible is the proximity of i to 1

[Swift]

That can be used to graph any function valid in two dimensions

Should be for a well behaved function. For instance if you try to graph tan over pi/2 you'll get an error