Writing an equation in terms of specific variables where relationship is known.

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Jack 2021-12-27

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https://ww2.mathworks.cn/matlabcentral/answers/1618280-writing-an-equation-in-terms-of-specific-variables-where-relationship-is-known

编辑： Jack 2021-12-27

采纳的回答： Torsten

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So I am trying to specify what an equation is written in terms of, below is a simple example i have concoted.

Since i know r's relationship to t I could write F in terms of r or t. Is there a way of asking matlab to write a function in terms of specific variables? In this case I would want F in terms of m,a,b and r not t for example.

clear all

syms m a b t

r = a*b*t^2

r =

F = m * diff(r,t)

F =

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Torsten 2021-12-27

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syms m a b t r
t_eq = solve(r - a*b*t^2==0,t);
r = a*b*t^2;
F = m * diff(r,t);
F = subs(F,t,t_eq)

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Torsten 2021-12-27

编辑：Torsten 2021-12-27

I doubt it.

I think you will have to solve for the variable(s) you don't want the equation to be in terms of and afterwards substitute the corresponding expressions (only depending on the variables you want the equation to be in terms of) into the equation.

But someone might correct me here.

Jack 2021-12-27