Issue with align/alignat and equations

Question

I would appreciate help with this.

I'm trying to align a couple of equations but am having some issues. 1. With this code shouldn't the \wedge be properly aligned with the >. This happens for both alignat and align.

My objective would be to align these and have equal spacing between them and the expressions on either side.

%Edit: Add clarification on output

   if        d > d                25
 then        M > eta              26
 with  bla bla A O(bla bla)       27

Thanks in advance

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}

\begin{document}

  \begin{alignat}{5}
     \label{eq:test}
     \mathrm{iff}  \quad &&\frac{\partial L}{\partial\eta_2} \quad&>&&\quad\displaystyle\frac{\partial L}{\partial M} && \\
     \mathrm{then} \quad &&M                                 \quad&>&&\quad\sigma\eta_2  && \\
     \mathrm{with} \quad &&0 \le \eta_2 \le 1                \quad&\wedge&&\quad \mathrm{O}(\sigma) \le 1 \quad \blacksquare &&
 \end{alignat}

 \begin{align}
     \label{eq:test}
     \mathrm{iff}  \quad &&\frac{\partial L}{\partial\eta_2} \quad&>&\quad\displaystyle\frac{\partial L}{\partial M} && \\
     \mathrm{then} \quad &&M                                 \quad&>&\quad\sigma\eta_2  && \\
     \mathrm{with} \quad &&0 \le \eta_2 \le 1                \quad&\wedge&\quad \mathrm{O}(\sigma) \le 1 \quad \blacksquare &&
 \end{align}  
\end{document}

Answer 1

I'm not sure whether such alignments carry any meaning.

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{amsmath,amssymb}

\newcommand{\pder}[2]{\frac{\partial #1}{\partial #2}}

\begin{document}

\begin{alignat}{2}
\text{iff}  &\quad& \pder{L}{\eta_2}   &>\pder{L}{M}  \\
\text{then} &\quad& M                  &>\sigma\eta_2 \\
\text{with} &\quad& 0 \le \eta_2 \le 1 &\mathrel{\wedge}
   \mathrm{O}(\sigma) \le 1 \quad \blacksquare
\end{alignat}

\end{document}

Answer 2

The eqparbox package can help. Is this what you want? (I find the spacing a little weird…)?

\documentclass[11pt]{article}
\usepackage{amssymb}
\usepackage{makebox}
\usepackage{mathtools, nccmath}

\usepackage{eqparbox}

    \newcommand\eqmathbox[2][M]{\eqmakebox[#1]{$\displaystyle{}#2{}$}}

    \begin{document}

\begin{alignat}{5}
     \label{eq:test}
     \mathrm{iff} \quad &&\frac{\partial L}{\partial\eta_2} \quad&\eqmathbox{>}&&\quad\displaystyle\frac{\partial L}{\partial M} && \\
     \mathrm{then} \quad &&M \quad&\eqmathbox{>}&&\quad\sigma\eta_2 && \\
     \mathrm{with} \quad &&0 \le \eta_2 \le 1 \quad&\eqmathbox{\wedge} &&\quad \mathrm{O}(\sigma) \le 1 \quad \blacksquare &&
 \end{alignat}

 \begin{align}
     \label{eq:test}
     \mathrm{iff} \quad &&\frac{\partial L}{\partial\eta_2} \quad& \eqmathbox{>}&\quad\displaystyle\frac{\partial L}{\partial M} && \\
     \mathrm{then} \quad &&M \quad&\eqmathbox{>}&\quad\sigma\eta_2 && \\
     \mathrm{with} \quad &&0 \le \eta_2 \le 1 \quad&\eqmathbox{\wedge}&\quad \mathrm{O}(\sigma) \le 1 \quad \blacksquare &&
 \end{align}

 \end{document}

Answer 3

with align:

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{amsmath,amssymb}

\begin{document}
 \begin{align}
     \label{eq:test}
 \mathrm{iff}  &&
        \frac{\partial L}{\partial\eta_2}\     > &\ \dfrac{\partial L}{\partial M}  &&\\
 \mathrm{then}  &&
        M\                                     > &\ \sigma\eta_2                    &&\\
 \mathrm{with}  &&0
        \le \eta_2 \le 1\                \wedge  &\ \mathrm{O}(\sigma)\le 1\quad \blacksquare &&
 \end{align}
 \end{document}