[Tex/LaTex] Code for the Notation of Vector Projections

vector

What LaTex code do I use to get the notation on the left of this equation, that is the projection of vector a on vector v?

http://rypress.com/tutorials/mathml/media/vectors-and-functions/summary.png

Best Answer

Here is an option:

enter image description here

\documentclass{article}

% http://tex.stackexchange.com/q/169557/5764
\usepackage{mathtools}
\DeclarePairedDelimiter{\norm}{\lVert}{\rVert}
\newcommand{\vectorproj}[2][]{\textit{proj}_{\vect{#1}}\vect{#2}}
\newcommand{\vect}{\mathbf}

\begin{document}

\[
  \vectorproj[v]{a} = \frac{\vect{a} \cdot \vect{v}}{\norm{\vect{v}}^2} \vect{v}
\]

\end{document}

\vectorproj[<onvector>]{<ofvector>} can be supplied with an optional <onvector>.

Related Solutions

[Tex/LaTex] Labeling Drawing of Euclidean Vector

My solution to this would be to use PGF/Tikz, which is way nicer with rasterization. You could achieve the same drawing like this :

\begin{tikzpicture}[auto]
    \node (a) at (0,0)  {};
    \node (b) at (2,3)  {};
    \node (c) at (3,2)  {};

    \draw[->] (a) to node {u} (b);
    \draw[->] (b) to node {u-v} (c);
    \draw[->] (a) to node {v} (c);
\end{tikzpicture}

Or something of the sort, you can consult the PGF/Tikz manual which is full of nice examples (for instance summing coordinates).

And no, an EPS file won't give a nicer result, since it has to be scaled at some point, and second it is not easy to change your diagram once you've included it with the EPS method.

[Tex/LaTex] Vector notation in siunitx

One way to do this is to simply use:

\vec{F} = (\num{-3.24e-20}\hatx + \num{4.56e-18}\haty) \,\si{\newton}