\begin{tikzpicture}[scale=1, help lines/.style={black!30,very thin}]
	\clip (-1.1,-1.1) rectangle (4.1,4.01);

	% Grid
	\draw[help lines] (-1,-1) grid +(5,5);

	% \vec u
	\draw[very thick] [->] (0,0) -- (3,3);
	\draw (1.5,1.5) node[anchor=north west] {$\vec u$};

	% \hat i
	\draw[thick] [->] (0,0) -- ++(1,0);
	\draw (0.5,0) node[anchor=north] {$\hat i$};

	% \hat j
	\draw[thick] [->] (0,0) -- ++(0,1);
	\draw (0,0.5) node[anchor=east] {$\hat j$};

	\draw (0.5,0.25) node {$\theta$};
\end{tikzpicture}
