Math Is Fun Forum

kdria041

Member

Registered: 2005-12-27

Posts: 4

Curve Equation

0    0
1    0
2    0
3    10
4    83
5    170
6    300
7    500
8    750
9    1150
10    1500
11    1750
12    1800

Can anyone give me the formula for this plot?  The numbers are not absolute, as they were taken off a small graph, so a formula that would aproximate this curve is ok.  THANKS!
asympyotes 0, 1800

This is the curve for which I need an equation:

John E. Franklin

Member

Registered: 2005-08-29

Posts: 3,588

Re: Curve Equation

Here is a silly answer that uses operators that are probably disallowed in algebra in this fashion for some reason or other.

y=0(x<3) + (3 ≤ x<11)(1800/(11-3))(x-3) + (x ≥ 11)1800

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igloo myrtilles fourmis

MathsIsFun

Administrator

Registered: 2005-01-21

Posts: 7,713

Re: Curve Equation

The tanh(x) function has two horizontal asymptotes, it could be adapted possibly.

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"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman

krassi_holmz

Real Member

Registered: 2005-12-02

Posts: 1,905

Re: Curve Equation

arctan(x) also has two horizontal asymptotes.
But I think that these functions cannot be adapted for this graph, because it is not symmetric.

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IPBLE:  Increasing Performance By Lowering Expectations.

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: Curve Equation

Why not this for solution?:

if:3<x<12 y=((1/logx^3)+1)*x^3

kdria posted that meaning to reply to this topic, but accidentally starting a new one instead.

You can reply using the 'post reply' button. ;)

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Why did the vector cross the road?
It wanted to be normal.

seerj

Member

Registered: 2005-12-21

Posts: 42

Re: Curve Equation

arctan(x) also has two horizontal asymptotes.
But I think that these functions cannot be adapted for this graph, because it is not symmetric.

Yes I quote him! You can use arctan(x) by creating your own function
For example try to plot a function like this:

2*atan(x-3)+3

seerj

Member

Registered: 2005-12-21

Posts: 42

Re: Curve Equation

arctan(x) also has two horizontal asymptotes.
But I think that these functions cannot be adapted for this graph, because it is not symmetric.

Yes I quote him! You can use arctan(x) by creating your own function
For example try to plot a function like this:

2*atan(x-3)+3

Or wait also tanh(x) is good. I think is perfect for your case

Try to plot it

tanh(x-3/5)+1

Last edited by seerj (2005-12-29 03:21:16)

krassi_holmz

Real Member

Registered: 2005-12-02

Posts: 1,905

Re: Curve Equation

Yes, yes.
And seerj's curves are close.

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IPBLE:  Increasing Performance By Lowering Expectations.