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Ok I try to get and install it.
Thank you so very much for your prompt response.
Regards

oh well I was using PDFLatex icon and getting the discussed error, however, now i 've run it from command line as guided by you. See the snapshot, you may be able to suggest something now, i think,

well, I get the error shown in my first post when use PDF texify or PDF Latex icons directly.
No other window appears.
The command window or error shown in my second post appears when I use to compile it using TEX icon.
Sorry for poor quality snapshots kindly see the attached.
I am not sure that I ...

yes I tried but no use.....
showing undefined 'control sequence \documentclass'
kindly see the snapshot

I am a good LaTeX user and using it for almost five years.

But this is the most frequent, weird and incomprehensible problem that I could find ever. Now I have to write my thesis but any of my LaTeX files (even the sample/example documents) are not beeing compiled . I've a full installation of ...

Thanks alot.

Here is the equation code; ofcourse it must be aligned but i think i would be able to handle that issue, right now i just need the solution to the problem with numerator. Many thanks.

\begin{align}
\frac{\partial e_m}{\partial c_i}&=\varepsilon\left(\frac{\left(\sum_{i=1}^R\beta_i\prod_{j=1}^L\exp ...

Plz let me know the solution to this problem if anybody knows. I need it badly and urgently .

Hello,
I have to write an equation with a fraction. But the problem is that the numerator of the fraction is very long so that i have to break it in two lines. Please let me know how can i do that?

Many thanks and best regards in advance.

Many thanks , it's working.