Writing on top of a long arrow

Question

I want to make the arrow in the numerator longer, like the one in the denominator and write $x$ on top of it. I'm using the package mathtools.

\[
    H_{1}(K_1)=\frac{\textrm{ker}(R \xrightarrow{x} R)}{\textrm{im}(0 \longrightarrow R)} \cong \textrm{ker}(R \longrightarrow R)= \frac{R}{xR}.
\]

A tip: If you indent lines by 4 spaces or [enclose words in backticks ```](http://meta.tex.stackexchange.com/q/863), they'll be marked as code, as can be seen in my edit. You can also highlight the code and click the "code" button (with "{}" on it). // By the way: \[ ... \] is better than $$ ... $$ for entering math mode. — ebosi, Dec 12 '16 at 13:40
You can do this: \xrightarrow{~x~} or this \xrightarrow{\,\,x\,\,} — Steven B. Segletes, Dec 12 '16 at 13:43
Thank you everyone. Appreciate all the help and suggestions. — Yeah, Dec 12 '16 at 14:13

Mico · Answer 1 · 2016-12-12T13:56:12.667

I suggest you load the extarrows package and use that package's \xlongrightarrow macro.

Aside: Since "ker" and "im" are math operators, do make them into objects of type mathop. The macro \ker is pre-defined; it's straightforward (using the \DeclareMathoperator tool) to set up \im as a math-op object as well.

\documentclass{article}
\usepackage{mathtools,extarrows}
\DeclareMathOperator{\im}{im}
\begin{document}
\[
    H_{1}(K_1)=\frac{\ker(R\xlongrightarrow{x}R)}{\im(0\longrightarrow R)} 
    \cong \ker(R\longrightarrow R)= \frac{R}{xR}.
\]
\end{document}

score 0 · Accepted Answer · answered Dec 12 '16 at 13:44

0

(memoir is unrelated, just my goto class)

\documentclass[a4paper]{memoir}
\usepackage{amsmath,amssymb}
\DeclareMathOperator\im{im}
\begin{document}
\[
H_1(K_1) = \frac{\ker(R\xrightarrow{x} R)}{\im(0\to R)}
\]
\end{document}

answered Dec 12 '16 at 13:44

daleif

54,450

@Yeah - You wrote in your query that "I want to make the arrow in the numerator longer, like the one in the denominator..." Yet you accepted an answer that works by performing the exact opposite operation: Making the arrow in the denominator shorter - as short, in fact, as the arrow in the numerator of your original posting. Should you maybe rewrite your stated objective to avoid confusion as to what you were trying to achieve? – Mico Dec 12 '16 at 14:59

Writing on top of a long arrow

2 Answers2