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\documentclass[14pt,english]{article}
\usepackage[margin=0.8in]{geometry}
 \usepackage{amsmath}

\begin{document}





\begin{align}


&=\sum_{i=1}^{n}\lambda\rho\sin(x_i-X_i)-\dfrac{1}{c}\sum_{i=1}^{n}\dfrac{-\beta_i\eta_1\sin(y_i-\beta_i X_i)+\beta_i\eta_2\cos(y_i-\beta_i X_i)}{1-\alpha_1\cos(y_i-\beta_i X_i)-\alpha_2\sin(y_i-\beta_i X_i)}
\end{align}
\end{document}
moewe
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Rita ana
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1 Answers1

3

If your document really look like described, the error is here:

\begin{align}

&=

An empty line means new paragraph, which is forbidden inside math.

Moreover, without additional package, e.g. extarticle in place of article, your option 14pt will be ignored and all document will be in 10pt.

Przemysław Scherwentke
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