amsmathequationsnumbering
I have the following code:
$\begin{aligned}[t]
P\{X\in A\}&=\int_A\int_{-1}^1 f(x, y)dydx \\
&=\int_A\int_{-1}^1\frac{1}{4}dydx \\
&=\int_A\frac{1}{4}\times 2dx \\
&=\int_A\frac{1}{2}dx
\end{aligned}$
I want to label the last line as (2). How do I do this?
You may want to use split, along with the tbtags option to amsmath.
\documentclass{article}
\usepackage[tbtags]{amsmath}
\begin{document}
\begin{equation}
\begin{split}
x ={} & 22+2 \\
={} &5+3\\
&-3+4\\
&+15-0
\end{split}
\end{equation}
\end{document}
If you want two numbers, then use split inside align: the alignment point will be inherited in the inner environment:
\documentclass{article}
\usepackage[tbtags]{amsmath}
\begin{document}
\begin{align}
x ={} & 22+2 \\
\begin{split}
={} & 5+3\\
&-3+4\\
&+15-0
\end{split}
\end{align}
\end{document}
I think flalign* and \intertext{} are very good for you.
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{flalign*}
& & T_{Loop Filter}(s)&=K_{p}+\frac{K_{i}}{s} & & \\
\intertext{The overall transfer function of given PLL can be given as}
& & \frac{{\phi}_{c}(s)}{{\phi}(s)}&=\frac{T_{Loop Filter}(s)*\frac{1}{s}}{1+\frac{T_{Loop Filter}}(s)*\frac{1}{s}} & & \\
& & \frac{\phi_{c}(s)}{\phi(s)}&=\frac{K_{p}(s)+K_{i}}{s^{2}+K_{p}(s)+K_{i}} & &
\intertext{In general transfer function for a second order closed loop control system is given as}
& & T_{second order}&=\frac{{\omega}^2+{2{\delta}}{\omega}s}{s_{2}+2{\delta}{\omega}s+{\omega}^{2}} & & \\
& \rlap{\text{On comparing}} & {\omega}&={sqrt{K_i}} {\delta}=\frac{K_p}{2\sqrt{K_{i}}} & &
\end{flalign*}
\end{document}
Best Answer
What you need is
split. The number will be assigned automatically.Note how I got the right spacing for the differential symbols. If you change your mind and prefer a vertically centered number, remove the
tbtagsoption.