# Cropping a TikZ display

I have a display of two intersecting lines and a ray starting at the intersection of the two lines. I use path commands

\path[name path = left.side] (-3.75,-3.75) -- (-3.75,3.75);


and

\path[name path = right.side] (3.75,-3.75) -- (3.75,3.75);


and the intersections package to draw these lines between two vertical lines. How do I crop the top and bottom space? I only include the command

\draw (current bounding box.south west) grid (current bounding box.north east);


to show how much wasted space there is.

\documentclass{amsart}

\usepackage{tikz}
\usetikzlibrary{calc,angles,positioning,intersections,quotes}

\usepackage{mathtools}

\usepackage{pgfplots}
\pgfplotsset{compat=1.11}

\begin{document}

\begin{tikzpicture}

\coordinate (Q) at (0,0);
\node[fill=white,circle,inner sep=0pt] (Q-label) at ($(Q)+(-90:10pt)$) {$Q$};

\coordinate (R) at ($(Q) +(3.75,0)$);
\draw[-latex] (Q) -- (R);
\node at ($(R)+(0:10pt)$) {$m$};

\path[name path = ell.up] (0,0) -- (25:5);
\path[name path = ell.down] (0,0) -- (-155:5);
\path[name path= k.up] (0,0) -- (165:5);
\path[name path = k.down] (0,0) -- (-15:5);

%The following commands are for placing drawing the lines, placing the
%arrowheads at the ends of the line segments. The drawn lines are to be
%bound between the vertical lines $x = -3.75$ and $x = 3.75$. Since
%$\ell$ has the steeper slope, the height of the bounding box is determined
%by $\ell$.
\path[name path = left.side] (-3.75,-3.75) -- (-3.75,3.75);
\path[name path = right.side] (3.75,-3.75) -- (3.75,3.75);

\path[name intersections={of= left.side and ell.down, by=aa/ell}];%left.side.ell.down
\path[name intersections={of= right.side and ell.up, by=bb/ell}];%right.side.ell.up

\draw[draw=blue!30,latex-latex] (aa/ell) -- (bb/ell);

\path[name intersections={of= left.side and k.up, by=aa/k}];%left.side.k.down
\path[name intersections={of= right.side and k.down, by=bb/k}];%right.side.k.up

\draw[draw=green!50,latex-latex] (aa/k) -- (bb/k);

%These commands put the labels on lines $\ell$ and $k$.
\node at ($(bb/ell)+(25:10pt)$) {$\ell$};
\node at ($(bb/k)+(-15:10pt)$) {$k$};

%These commands label the angles.
\path pic[angle radius=5mm,"$\scriptstyle{40}$",angle eccentricity=1.25] {angle = aa/k--Q--aa/ell};
\path pic[angle radius=10mm,"$\scriptstyle{25}$",angle eccentricity=1.25] {angle = R--Q--bb/ell};
\path pic[angle radius=10mm,"$\scriptstyle{x}$",angle eccentricity=1.25] {angle = bb/k--Q--R};

%This command draws a dot at point Q; the dot is drawn over the two lines.
\draw[fill] (Q) circle (1.5pt);

\draw[line width=0.1pt, draw=gray!25] (current bounding box.south west) grid (current bounding box.north east);
\end{tikzpicture}

\end{document}

• You are missing a lot of overlay keys for those long 5s and 3.75s. And basically you are drawing something that can be done in 4 lines of line drawing no? – percusse May 27 '15 at 23:22

Option overlay helps:
\path[overlay, name path = left.side] (-3.75,-3.75) -- (-3.75,3.75);

And overlay applied to the other \path[name ...] commands as well: