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when i 'm trying to run this mfile it is giving the following error ??? Undefined function or method 'solve' for input arguments of type 'double'. Error in ==> tofindx at 14 . can anyone please help me to solve the problem? thanku

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Aiswaria
Aiswaria 2013-2-1
关闭： MATLAB Answer Bot 2021-8-20
clc;
clear all;
x=0;
f=input('force:');
rho=input('rho:');
D=input('diameter:');
Cd=input('Cd:');
Cm=input('Cm:');
w=input('w:');
u=input('u:');
a=input('a:');
t=0.1;
S=solve(((0.5*rho*Cd*D*abs(u+x*w*sin(w*t))*(u+x*w*sin(w*t)))+(rho*pi*D^2*Cm*(a+x*cos(w*t)*w^2)/4)+(rho*pi*D^2*w^2*x*cos(w*t)/4))==f,x);

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回答（1 个）

Walter Roberson
Walter Roberson 2013-2-1
编辑：Walter Roberson 2013-2-1
You have not made "x" a symbolic variable: instead you made it a numeric variable when you used "x=0" Use
syms x
If it complains that there is no command syms for arguments of type char, then you either do not have the Symbolic toolbox installed or you do not have it licensed.
If, after you use "syms x", you get a complaint about not being able to convert from syms to double, then you are using an older version of MATLAB that does not accept "==" in expressions. If that happens to you then change your expression from the form
A == B
to the form
(A) - (B)
with no "==" in it.

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