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Definiing two functions (mathematica)

by rbnphlp
Tags: definiing, functions, mathematica
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rbnphlp
#1
Feb25-12, 10:57 AM
P: 54
I need to define two functions for a molecule with speed s.
a)it has a horizontal velocity between -s and s
b) v , the vertical velocity between +Sqrt[s^2-u^2] and -Sqrt[s^2-u^2]

This is what I have done
for a)
f[s_]:=RandomReal[{-s,s}]
for b)
g[s_,u_]:=RandomReal[{-Sqrt[s^2-u^2],+Sqrt[s^2-u^2]}]
now , If I enter f[2] I get u, so I have s and u from first code. How do I use these values in the second code (without manually inputting them)?

Thanks a bunch
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jackmell
#2
Feb25-12, 12:07 PM
P: 1,666
You mean just

g[s,f[s]] ?
rbnphlp
#3
Feb25-12, 12:20 PM
P: 54
Quote Quote by jackmell View Post
You mean just

g[s,f[s]] ?
Yes ,thats what I want ..But how do I put into mathematica ?

If just insert what you have written I get

RandomReal::unifr: "The endpoints specified the uniform distribution range are not real valued

I also Tried,

g[s_] := RandomReal[{-Sqrt[s^2 - f[s]^2], +Sqrt[s^2 - f[s]^2]}]
However , what it does in this case is , finds f[s] for -Sqrt[s^2 - f[s]^2] and +Sqrt[s^2 - f[s]^2] seperately , so I get different f[s] in that case..

Any ideas?

jackmell
#4
Feb25-12, 01:41 PM
P: 1,666
Definiing two functions (mathematica)

I believe that's because the arguments to RandomReal have to be real. But for example if I entered:

g[2,f[3]]

the argument passed to Sqrt results in a complex number. Either need to make sure s^2-u^2 is real or either use RandomComplex.


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