Negative coordinates in TikZ

I am trying to use Tikz. Unfortunately, something seems to go wrong when I use negative coordinates: the last line of the code

\begin{tikzpicture}[scale=2]
\draw [->] (-1,0) -- (3.2,0);
\draw [->] (0,-1.125) -- (0,3.2);
\draw (-0.75 : -0.5)--(1.5,2.25);
\end{tikzpicture}


draws a line starting from (-0.75,0), not from (-0,75,-0.5). What gives?

Try this

\begin{tikzpicture}[scale=2]
\draw [->] (-1,0) -- (3.2,0);
\draw [->] (0,-1.125) -- (0,3.2);
%\draw (-0.75 : -0.5)--(1.5,2.25); % :' gives you polar coordinate, but
% you are looking for canva coordinate
% (Cartesian coordinate), so you need
% ,' in the place of :'.
\draw (-0.75 , -0.5)--(1.5,2.25);
\end{tikzpicture}
`
• Thanks! That was embarassing :) – H A Helfgott May 8 at 8:30