# Equation environment

I use texmaker program. I can not jump up to next line by using symbol \\ in equation environment:

$$....$$


I could do it before but now I can't. In other environments, I can do it. Could you show me how to solve this problem, please?

• You can't do it in the equation environment. Use one of the amsmath's environment: align, gather, multine and the like. – Bernard Nov 17 '14 at 9:50
• Yes, I am using align environment. But I want to know why I cann't do it in equation evr. Thank you very much! – user164162 Nov 17 '14 at 9:53
• Because equation is not designed to do it! – user11232 Nov 17 '14 at 10:03
• @Bernard -- all of the amsmath multi-line structures are built in essentially the same way. equation is different because it is defined essentially the same as in basic latex; only a * form has been added. – barbara beeton Nov 17 '14 at 13:08
• Unfortunately, MathJax allows \\ in equation, which can be grossly misleading to its users when they switch to proper LaTeX. – egreg Nov 17 '14 at 13:13

You have never been able to use \\ in the equation environment. The usage of it in that environment has always produced errors, because equation can just contain one line. An exception is the usage of internal auxiliary environments such as split, aligned or alignedat, but in this case \\ would not be in the equation environment, but in the auxiliary one.

Load amsmath with \usepackage{amsmath} in any document that has math.

If you want to display two consecutive equations as if each is in equation, then use gather:

\begin{gather}
\cosh^{2} t - \sinh^{2} t = 1 \\
2\sinh^{2} t + 1 = \sinh 2t
\end{gather}


If you want to highlight the equals signs, use align:

\begin{align}
2\sinh t &= e^{t}-e^{-t} \\
2\cosh t &= e^{t}+e^{-t}
\end{align}


Note: MathJax allows using \\ in equation or $...$. I think this is a bad mistake, because it makes for unportable code.