what is wrong in this code

Question

Angad Singh Agarwal 2017-2-12

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/324564-what-is-wrong-in-this-code

评论： Torsten 2017-2-13

syms t;
y=(3.7).*(10).^17;
y=3.88*(10).^16.*(t).^(1.5).*exp(-7000./t);
k=solve(y);

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Stephen23 2017-2-12

@Angad Singh Agarwal: I formatted your code correctly by selecting the code text and then clicking the {} Code button. Next time you can do this yourself.

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Answer 1

sjoerd 2017-2-12

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https://ww2.mathworks.cn/matlabcentral/answers/324564-what-is-wrong-in-this-code#answer_254412

编辑：sjoerd 2017-2-12

在 MATLAB Online 中打开

Althought it is not completely clear to me what your question/problem exactly is, I will give it a try I assumed that you want to solve the following equation for t:

3.7e17 = 3.88e16*(t)^(1.5)*exp(-7000./t)

Please note the use of 'e' for the scientific notations which makes its way shorter. Next to this I removed the dots because no need to solve this element wise (only scalar calculations).

The main problem with your code is that you first assign a value to to 'y' and then overwrite this value with the full equation. So introducing a different variable gives the following.

syms t;
result=3.7e17;
y=3.88e16*(t)^(1.5)*exp(-7000/t);
k=solve(y==result);

And this solves for t, (it will give warning that it is not symbolically solved but a numerical approximation is used).

k = 833 (approximately)

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Angad Singh Agarwal 2017-2-13

编辑：per isakson 2017-2-13

在 MATLAB Online 中打开

showing following error

??? Error using ==> char
Conversion to char from logical is not possible.
Error in ==> solve>getEqns at 189
   vc = char(v);
Error in ==> solve at 67
[eqns,vars] = getEqns(varargin{:});
Error in ==> Untitled2 at 4
k=solve(y==result); 
??? Error using ==> char
Conversion to char from logical is not possible.
Error in ==> solve>getEqns at 189
   vc = char(v);
Error in ==> solve at 67
[eqns,vars] = getEqns(varargin{:});
Error in ==> Untitled2 at 4
k=solve(y==result); 
??? Error using ==> char
Conversion to char from logical is not possible.
Error in ==> solve>getEqns at 189
   vc = char(v);
Error in ==> solve at 67
[eqns,vars] = getEqns(varargin{:});
Error in ==> Untitled2 at 4
k=solve(y==result);

sjoerd 2017-2-13

I think you need to give us a little bit more information, which Matlab version do you use? I am using R2015a and it works fine. Furthermore showing a single error stack is also fine ;)

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Answer 2

Torsten 2017-2-13

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https://ww2.mathworks.cn/matlabcentral/answers/324564-what-is-wrong-in-this-code#answer_254544

在 MATLAB Online 中打开

syms t
result=3.7e17;
y=3.88e16*(t)^(1.5)*exp(-7000/t);
k=solve(y==result,t);

Best wishes

Torsten.