TikZ-PGF – Problems with TikZ Calculations

calculationscoordinatestikz-pgf

When can I use functions and do calculations in TikZ?
How do I make this work:

\draw (0,0) arc(0:90:sqrt(15)); %not ok

why is this working:

\draw (0,0) arc(0:asin(1):5); %ok

with \usetikzlibrary{calc} is this:

 \draw (0,0) -- ($ (4,0) + sqrt(7)*(0,1) $);  %ok

the only way to do single coordinate calculations? why is this

 \draw (0,0) -- ($ (4,sqrt(7)) $);  %not ok

not working?

Minimal example:

\documentclass{minimal}
\usepackage{tikz}
\usetikzlibrary{calc}
\begin{document}
\begin{tikzpicture}
\draw (0,0) arc(0:90:sqrt(15));              %not ok
\draw (0,0) arc(0:asin(1):5);                %ok
\draw (0,0) -- ($ (4,0) + sqrt(7)*(0,1) $);  %ok
\draw (0,0) -- ($ (4,sqrt(7)) $);            %not ok
\end{tikzpicture}
\end{document}

Best Answer

You need to wrap the expression into { } to hide the second pair of ( ) from the TeX parser. Without the { } a ( will be closed by the next ) even if it belongs to another (. This means arc(0:90:sqrt(15)) will be taken as arc(0:90:sqrt(15) without the second ). This causes basically two errors, one in the expression because it misses the ) and another one in the \draw path which doesn't know what to do with a single ). With the { } it works because any { must be closed first with a } before the ) is taken.

\documentclass{article}

\usepackage{tikz}
\usetikzlibrary{calc}

\begin{document}

\begin{tikzpicture}
    \draw (0,0) arc(0:90:{sqrt(15)}); %now ok
    \draw (0,0) arc(0:{asin(1)}:5); %ok
    \draw (0,0) -- ($ (4,0) + sqrt(7)*(0,1) $);  %ok
    \draw (0,0) -- ($ (4,{sqrt(7)}) $);  %now ok
\end{tikzpicture}

\end{document}
Related Question