Math & Science ⇒ Error when I'm trying to align equation at =

[marcoesteves]

Hello People,

I wanna align equation at = signal just to be easy to read, and beautifull

THis is my code, and I get an error.

Code: Select all

\begin{equation}
\label{eq1d_e1_bn_calc2}
\begin{align*}
{b_n} &= \frac{2}{L}\left[ {\int_0^{\frac{L}{2}} {x\sin \frac{{n\pi x}}{L}dx + \int_{\frac{L}{2}}^L {(L - x)\sin \frac{{n\pi x}}{L}dx} } } \right]\\
 	  &= \frac{2}{L}\left[ {{{\left( {\frac{L}{{n\pi }}} \right)}^2}\sin \frac{{n\pi x}}{L} - \frac{L}{{n\pi }}x\cos \frac{{n\pi x}}{L}} \right]_0^{\frac{L}{2}} + \frac{2}{L}\left[ {L\left( {\frac{L}{{n\pi }}} \right)\left( { - \cos \frac{{n\pi x}}{L}} \right) - {{\left( {\frac{L}{{n\pi }}} \right)}^2}\sin \frac{{n\pi x}}{L} + \frac{L}{{n\pi }}x\cos \frac{{n\pi x}}{L}} \right]_{\frac{L}{2}}^L.
\end{align*}
\end{equation} 

the error is,
! Package amsmath Error: Erroneous nesting of equation structures;

[localghost]

Actually the error message is very clear. You mustn't nest these two math environments. Replace align* with aligned. See the amsmath manual for details or the excellent »Math mode« document. And by the way, you shouldn't use so much unnecessary curly braces.


Thorsten

[bimalastha]

Try removing align and see if it works...

\begin{equation}
\label{eq1d_e1_bn_calc2}
%remove this \begin{align*}
{b_n} &= \frac{2}{L}\left[ {\int_0^{\frac{L}{2}} {x\sin \frac{{n\pi x}}{L}dx + \int_{\frac{L}{2}}^L {(L - x)\sin \frac{{n\pi x}}{L}dx} } } \right]\\
&= \frac{2}{L}\left[ {{{\left( {\frac{L}{{n\pi }}} \right)}^2}\sin \frac{{n\pi x}}{L} - \frac{L}{{n\pi }}x\cos \frac{{n\pi x}}{L}} \right]_0^{\frac{L}{2}} + \frac{2}{L}\left[ {L\left( {\frac{L}{{n\pi }}} \right)\left( { - \cos \frac{{n\pi x}}{L}} \right) - {{\left( {\frac{L}{{n\pi }}} \right)}^2}\sin \frac{{n\pi x}}{L} + \frac{L}{{n\pi }}x\cos \frac{{n\pi x}}{L}} \right]_{\frac{L}{2}}^L.
%remove this \end{align*}
\end{equation}

[marcoesteves]

Thanks,
But it's easier use aligned. It works too

Try removing align and see if it works...

\begin{equation}
\label{eq1d_e1_bn_calc2}
%remove this \begin{align*}
{b_n} &= \frac{2}{L}\left[ {\int_0^{\frac{L}{2}} {x\sin \frac{{n\pi x}}{L}dx + \int_{\frac{L}{2}}^L {(L - x)\sin \frac{{n\pi x}}{L}dx} } } \right]\\
&= \frac{2}{L}\left[ {{{\left( {\frac{L}{{n\pi }}} \right)}^2}\sin \frac{{n\pi x}}{L} - \frac{L}{{n\pi }}x\cos \frac{{n\pi x}}{L}} \right]_0^{\frac{L}{2}} + \frac{2}{L}\left[ {L\left( {\frac{L}{{n\pi }}} \right)\left( { - \cos \frac{{n\pi x}}{L}} \right) - {{\left( {\frac{L}{{n\pi }}} \right)}^2}\sin \frac{{n\pi x}}{L} + \frac{L}{{n\pi }}x\cos \frac{{n\pi x}}{L}} \right]_{\frac{L}{2}}^L.
%remove this \end{align*}
\end{equation}

[localghost]

[…] It works […]

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