\begin{tikzpicture} \tkzInit[xmax=9,xstep=3,ymax=4] \tkzGrid[xstep=1,ystep=pi/2,sub, subxstep=1,subystep=pi/4] \tkzLabelX[label=$t$,orig=false,frac=3, below=6pt,font=\scriptsize] \tkzLabelY[trig=2,font=\scriptsize] \end{tikzpicture}