# what is wrong in this code

19 views (last 30 days)
Angad Singh Agarwal on 12 Feb 2017
Commented: Torsten on 13 Feb 2017
syms t;
y=(3.7).*(10).^17;
y=3.88*(10).^16.*(t).^(1.5).*exp(-7000./t);
k=solve(y);

#### 1 Comment

Stephen Cobeldick on 12 Feb 2017
@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.

sjoerd on 12 Feb 2017
Edited: sjoerd on 12 Feb 2017
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)

Angad Singh Agarwal on 13 Feb 2017
thanks a lot.
Angad Singh Agarwal on 13 Feb 2017
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 on 13 Feb 2017
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 ;)

Torsten on 13 Feb 2017
syms t
result=3.7e17;
y=3.88e16*(t)^(1.5)*exp(-7000/t);
k=solve(y==result,t);
Best wishes
Torsten.

Angad Singh Agarwal on 13 Feb 2017
??? 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); ??? 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,t); ??? 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,t); ??? 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,t); ??? 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,t); ??? 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,t); ??? 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,t);
Torsten on 13 Feb 2017
You seem to use an older MATLAB version.
Take a look into your documentation to see how to use "solve" for your release.
Best wishes
Torsten.