Problem

I have several lines in a proof of mine, and I want to align several terms as shown:

Output

I can achieve the following using phantom where needed:

MWE

documentclassextarticle

usepackageamsmath,bbm,bm,amssymb,amsthm,mathtools,cleveref,physics,letltxmacro

% For usage in align environments. 
newcommandphantomrel[1]mathrelphantom#1
newcommandphantombin[1]mathbinphantom#1

begindocument
beginalign*
A
& = textseveral short lines\
& = textsome very long line which takes up most of the width of the page \ 
& = textseveral short lines \
& = B + mathbbE(absa + b + c + d) qquad text(typically too long for a single line) \
& leq B + mathbbE(absa) \ % Using the triangle inequality.
& phantomrelleq phantomB + mathbbE(absb) \
& phantomrelleq phantomB + mathbbE(absc) \
& phantomrelleq phantomB + mathbbE(absd) \
endalign*
enddocument

However, I am weary that this doesn't seem very scalable if I were to find an error and need to change B to a wider set of symbols, and would like to avoid falling into a copy/paste loop.

I am using phantomrel and phantombin because of a previous question of mine

Thinking of a better writing pattern my first two thoughts were:

• Use an aligned within the original align.


• Use an array.

Using an array?

beginalign*
A
& = textseveral short lines\
& = textsome very long line which takes up most of the width of the page \ 
& = textseveral short lines \
& = B + mathbbE(absa + b + c + d) qquad text(typically too long for a single line) \
& leq B 
beginarray[t]r
 + mathbbE(absa) \
 + mathbbE(absb) \
 + mathbbE(absc) \
 + mathbbE(absd) \
endarray
endalign*

Although this has the + symbols too far offset because of the array margin.

Use aligned?

beginalign*
A
& = textseveral short lines\
& = textsome very long line which takes up most of the width of the page \ 
& = textseveral short lines \
& = B + mathbbE(absa + b + c + d) qquad text(typically too long for a single line) \
& 
beginaligned
leq B & + mathbbE(absa) \ % Using the triangle inequality.
& + mathbbE(absb) \
& + mathbbE(absc) \
& + mathbbE(absd) 
endaligned
endalign*

Almost, but the alignment is a bit off and I am not sure why.

Why not just use aligned for the whole thing?

I can't figure out how I would handle the very long lines without some selective use of mathclap (or similar), and would rather keep my use of ampersands to a minimum.

I added so you get relation spacing

documentclassextarticle

usepackageamsmath,bbm,bm,amssymb,amsthm,mathtools,cleveref,physics,letltxmacro

% For usage in align environments. 
newcommandphantomrel[1]mathrelphantom#1
newcommandphantombin[1]mathbinphantom#1

begindocument
beginalign*
A
& = textseveral short lines\
& = textsome very long line which takes up most of the width of the page \ 
& = textseveral short lines \
& = B + mathbbE(absa + b + c + d) qquad text(typically too long for a single line) \
& 
beginaligned
leq B & + mathbbE(absa) \ % Using the triangle inequality.
& + mathbbE(absb) \
& + mathbbE(absc) \
& + mathbbE(absd) 
endaligned
endalign*enddocument

I have no problem with aligned (measure precision: 0.1pt) and this very code. Unrelated: I removed the unnecessary packages.

documentclassextarticle

usepackagebm,amssymb, amsthm, mathtools, cleveref, physics, letltxmacro

% For usage in align environments.
newcommandphantomrel[1]mathrelphantom#1
newcommandphantombin[1]mathbinphantom#1

begindocument

beginalign*
A
& = textseveral short lines\
& = textsome very long line which takes up most of the width of the page \
& = textseveral short lines \
& = B + mathbbE(absa + b + c + d) qquad text(typically too long for a single line) \
& leq B beginaligned[t] & + mathbbE(absa) \ % Using the triangle inequality.
 & + mathbbE(absb) \
 & + mathbbE(absc) \
 & + mathbbE(absd)
endaligned
endalign*

enddocument 

I would use a top-aligned aligned environment (pun intended) inside the align* environment.

Separately, I would also try to de-clutter the appearance of the equations by using fewer pairs of parentheses.

documentclassextarticle

usepackagemathtools,bbm,bm,amssymb,amsthm,physics,
 letltxmacro,cleveref % load 'cleveref' last
DeclareMathOperatorEmathbbE % expectation operator

begindocument
beginalign*
A
&= textseveral short lines\
&= textsome very long line which takes up most of the width of the page \ 
&= textseveral short lines \
&= B + Eabsa + b + c + d qquad text(typically too long for a single line) \
&leq B 
beginaligned[t]
 &+ E absa \ % by triangle inequality
 &+ E absb \
 &+ E absc \
 &+ E absd 
endaligned
endalign*
enddocument