Problem with XYZ-Coordinate Systems

Question

Perhaps I made a mistake with the syntax but I think I found a problem.

\documentclass[11pt]{scrartcl}
\usepackage{tikz}

\begin{document}

\begin{tikzpicture}[x = {(sin(-60) cm,-cos(-60) cm)},
                    y = {(0.866 cm,-0.5 cm)},
                    z = {(0cm,1cm)},
                    scale = 4]  
 \draw[->] (0,0,0) -- (1,0,0);
 \draw[->] (0,0,0) -- (0,1,0);
 \draw[->] (0,0,0) -- (0,0,1); 
 \draw circle (1);   
\end{tikzpicture} 

\end{document} 

I can use cos(60) for the second coordinate but I can't use sin(60) for the first one.

The question is how to work around this problem. What is the better way ?. I can use something like \xcoord with \pgfmathsetmacro\xcoord{sin(-60)} but perhaps there is a better way.

Answer 1

As Marco Daniel points out, you can make TikZ parse the expressions by enclosing them in curly braces. To interpret the result as centimetres, you can multiply your expression by * 1cm:

\documentclass[11pt]{article}
\usepackage{tikz}

\begin{document}

\begin{tikzpicture}[x = {({sin(-60)*1cm},{-cos(60)*1cm})},
                    y = {(0.866 cm,-0.5 cm)},
                    z = {(0cm,1cm)},
                    scale = 4]  
 \draw[->] (0,0,0) -- (1,0,0);
 \draw[->] (0,0,0) -- (0,1,0);
 \draw[->] (0,0,0) -- (0,0,1); 
 \draw circle (1);   
\end{tikzpicture} 

\end{document}