# Typeset a number with many digits in the align environment

Questions like this have been asked before, Here and here, but neither of these are within a math enviroment.

In context, I would like to type set the approximate solution to an integral to 100 digits.

\begin{align*}
I &=  \left[\left[\cos(1) + \operatorname{Si}(1)\right] - \left[-\left(\operatorname{Si}(0)-\frac{\pi}{2}\right)\right]\right] \\
I &=  \cos(1) + \operatorname{Si}(1) -\frac{\pi}{2} \\
I &\approxeq\num{-0.08441095055957388688903177037359518055393632433151889234592026720612077182783481670736342350213473343}
\end{align*}


For an minimal example, try to typeset

\begin{align}
\pi \approxeq 3.141592653589793238462643383279502884197169399375105820974944592307816406286208998628034825342117067982148086513282306647093844609550582231725359408128481117450284102701938521105559644622948954930381964428810975665933446128475648233786783165271201909145648566923460348610454326648213393607260249141273724587006606315588174881520920962829254091715364367892590360011330530548820466521384146951941511609433057270365759591953092186117381932611793105118548074462379962749567351885752724891227938183011949129833673362440656643086021394946395224737190702179860943702770539217176293176752384674818467669405132000568127145263560827785771342757789609173637178721468440901224953430146549585371050792279689258923542019956112129021960864034418159813629774771309960518707211349999998372978049951059731732816096318595024459455346908302642522308253344685035261931188171010003137838752886587533208381420617177669147303598253490428755468731159562863882353787593751957781857780532171226806613001927876611195909216420198938095257201065485863278865936153381827968230301952035301852968995773622599413891249721775283479131515574857242454150695950829533116861727855889075098381754637464939319255060400927701671139009848824012858361603563707660104710181942955596198946767837449448255379774726847104047534646208046684259069491293313677028989152104752162056966024058038150193511253382430035587640247496473263914199272604269922796782354781636009341721641219924586315030286182974555706749838505494588586926995690927210797509302955321165344987202755960236480665499119881834797753566369807426542527862551818417574672890977772793800081647060016145249192173217214772350141441973568548161361157352552133475741849468438523323907394143334547762416862518983569485562099219222184272550254256887671790494601653466804988627232791786085784383827967976681454100953883786360950680064225125205117392984896084128488626945604241965285022210661186306744278622039194945047123713786960956364371917287467764657573962413890865832645995813390478027590099465764078951269468398352
\end{align}


It appears that \num from siunitx doesn't work, nor does numprint.

Does anyone have a solution?

# Final Awnser

The final macro that I went with is:

\newcommand{\longnum}[1]{%
\parbox[t]{\dimexpr\linewidth-5em\relax}{\num[group-separator={\egroup\egroup\)\egroup\,\linebreak[0]\bgroup$$\iffalse$$\fi\bgroup\bgroup}]{#1}\dots}%
}


This will only work for 8.5in width paper and equations of the form X = . To make it work for other places, change the -5em. Using linegoal did not work for me, as it made the equation not fit the margins.

Using the siunitx solution from How to typeset large numbers and the linegoal solution from my half-baked solution to Compute remaining horizontal space in align environment we can get the following.

You can un-outcomment the \ifmeasuring@\else and \fi segments to see a version where the math content is somewhat centered, the number though goes until the right edge of the text.

Also, this does not account for an equation number, especially with \ifmeasuring@, the equation number will be typeset way in the margin.

## Code

\documentclass{article}
\usepackage{amsmath,siunitx,amssymb,linegoal}
\usepackage[showframe,pass]{geometry}
\makeatletter
\newcommand*\longnum[2][]{%
%  \ifmeasuring@\else