hm... but why it does not work?
\be
\begin{split}
P(t)=cos\theta J_0(\alpha) + 2 \cos \theta \sum_{n=1}^\infty J_{2n}(\alpha)\cos[2n f_0 t +l_0] \\
&&-2\sin\theta \sum_{n=1}^\infty J_{2n-1}(\alpha)cos[(2n-1) f_0 t +l_0]
\end{split}
\label{equ:P_t_bessel}
\ee
Yes, Cristo! It works with your version,but What I have write - it is my long formula with a beginning bracket \left[ at the 1st line and
ended bracket \right] at the end of the whole formula
i don't understand what you meant... "You should repeat the \right. \\ left. procedure for all sets of...
can you write right version here?
this version for example doesn't work too!
\begin{eqnarray*}
U=U_0\cos[c_1 \cos(\omega t) + c_2 cos(\omega_1 t) + \phi] \\
& {} U=U_0 \cos\phi\left[|J_0(c_1)J_0(c_2)| + \sum_n |2J_0(c_2 )J_{2n}(c_1)|\cos 2n\omega t \\
& {} +\sum_k|2J_0(c_1 )J_{2k}(c_2)|\cos...
I read a lot literature how to provide dividing of the formulas to new lines,but it's work just on a short one good like 1st one and doesn't on main (2nd one)
\begin{equation}\begin{split}
\Psi = & \cos kz + i\sin kz + {} \\
& {} + \frac{f(\theta)}{r}
(\cos kr + i\sin kr)...