I am using text with in aligned environment as
\begin{equation} \begin{aligned} \Vert \Vert^2_F&= tr\{()\}\\ &=\Vert\Vert_F^2\\ \shortintertext{which after differentiation gives} \mathbf{a}&=[] \end{aligned} \end{equation} Things are fine, but the equation number is not aligned in center but at the bottom right to last equality $\mathbf{a}&=[]$.
How to align equation number somewhere middle right of whole equation environment.?
It's not common to place an equation number next to a line of text. To achieve this look, you could (a) use an align* environment so that no equation numbers show up on math-mode lines, and (b) set up a helper macro, called \showeq in the example below, that serves to insert a formatted equation number at the end of the line that contains text.
\documentclass{article} \usepackage{mathtools} \newcommand\showeq{\hspace{\fill}\refstepcounter{equation}(\theequation)} \begin{document} \begin{align*} \Vert \Vert^2_F&= tr\{()\} \\ &= \Vert\Vert_F^2 \\ \shortintertext{which after differentiation gives\showeq} \mathbf{a} &= [] \end{align*} \end{document} 