pgfplots画二维图真的很方便，多例比较

%直接PDFLATEX编译即可
documentclass[border=1mm]{standalone}
usepackage{tkz-euclide,pgfplots}
egin{document}
egin{tikzpicture}[domain=0:4]
kzInit[xmax=4.2,ymax=4.2,xmin=-1.2,ymin=-3.2,xstep=1]
kzGrid
kzAxeXY
draw[color=red] plot (x,x) node[right] {$f(x)=x$};
draw[color=orange,domain=-0.5:4] plot (x,{0.05*exp(x)}) node[right] {$f(x)=frac{1}{20}mathrm e^x$};
draw[color=blue,domain=0:4] plot (x,{sin(x r)}) node[right] {$f(x)=sin x$};
draw[color=blue!50,x=1cm,y=0.5cm,domain=-0.5:2.4] plot (x, {(x)^3-4*(x)+2}) node[right] {$f(x)=x^3-4x+2$};
end{tikzpicture}
end{document}

%直接PDFLATEX编译即可
documentclass[border=1mm]{standalone}
usepackage{tkz-euclide,pgfplots}
egin{document}
egin{tikzpicture}
egin{axis}[x=.5cm,xmin=0,ymin=0]
addplot[mark=none,smooth,red,thick] expression[domain=0:12]{exp(((x-6)^2)/(-9))};
addplot[mark=none,smooth,blue,thick] expression[domain=1:19]{exp(((x-10)^2)/(-25))};
addplot[mark=none,smooth,ultra thick] expression[domain=7.5:12]{exp(((x-6)^2)/(-9))};
addplot[mark=none,smooth,ultra thick] expression[domain=1:7.5]{exp(((x-10)^2)/(-25))};
addplot[dotted,mark=none]coordinates{(6,0)(6,1)};
addplot[dotted,mark=none]coordinates{(10,0)(10,1)(0,1)};
addplot[dashed,mark=none]coordinates{(7.5,0)(7.5,0.7788)(0,0.7788)};
ode[pin=-45:{$P$}] at (axis cs:0,0.7788) {};
ode[pin=135:{$P_x$}] at (axis cs:7.5,0) {};
end{axis}
end{tikzpicture}
end{document}

%直接PDFLATEX编译即可
documentclass[border=1mm]{standalone}
usepackage{tkz-euclide,pgfplots}
egin{document}
egin{tikzpicture}[domain=0:4]
draw[very thin,color=gray] (-0.1,-1.1) grid (3.9,3.9);
draw[->,>=angle 90] (-0.2,0) -- (4.2,0) node[right] {$x$};
draw[->,>=angle 90] (0,-1.2) -- (0,4.2) node[above] {$f(x)$};
%plot选项请看pgfmanual手册第224页
draw[color=red] plot (x,x) node[right] {$f(x)=x$};
draw[color=orange] plot (x,{0.05*exp(x)}) node[right] {$f(x)=frac{1}{20}mathrm e^x$};
%下面的sin函数，要注意弧度和度数单位的转换，手册第225页
draw[color=blue] plot (x,{sin(x r)}) node[right] {$f(x)=sin x$};
draw[color=blue,x=1cm,y=0.5cm,domain=-0.5:2.4] plot (x, {(x)^3-4*(x)+2}) node[right] {$f(x)=x^3-4x+2$};
end{tikzpicture}
end{document}

from: http://blog.sina.com.cn/s/blog_01ea595801013ig7.html