I am having a problem in aligning some symbols under an equation... This is the code:
\begin{align*}
D(\ldots,\,&tA^j,\,\ldots)=tD(\ldots,\,&A^j,\,\ldots).\\
& \uparrow & \uparrow \\
& k & k
\end{align*}
...and the output I get:
I also tried using the array environment instead, but still can't figure out how to put the arrow (and letter k) in the exact position. How should I do?
Thanks in advance.
P.S.
Same thing happens over here:
\begin{align*}
D(\ldots,\,A^k & +tA^j,\,\ldots) = D(\ldots,&\,A^k,\,\ldots) + D(\ldots,&\,tA^j,\,\ldots) \\
& \uparrow & \uparrow & \uparrow \\
& k & k & k
\end{align*}
which gives: