ClearAll;
$DefaultFont = {"Times-Roman",10};
Needs["Graphics`Graphics`"];
p = 621/25;
A = p/(2 Pi);
 
upper = Plot[Cos[x],{x,0,2 Pi},PlotPoints->100,
				PlotRange->{{0,25.05},{-1.01,1.01}},
				AxesOrigin->{-0.5,-1.1},
				Ticks->{Join[Table[10(i-1),{i,3}],{{2 Pi,FontForm["2p",{"Symbol",9}]},{p,"L"}}],{{-1,"-1"},{0,"0"},{1,"1"}}},
				AxesLabel->{"x","y"},
				PlotLabel->"(a) y = C(x)"];
lower = Plot[Cos[t/A],{t,0,p},PlotPoints->100,
				PlotRange->{{0,25.05},{-1.01,1.01}},
				AxesOrigin->{-0.5,-1.1},
				Ticks->{Join[Table[10(i-1),{i,3}],{{2 Pi,"L/A"},{p,"L"}}],{{-1,"-1"},{0,"0"},{1,"1"}}},
				AxesLabel->{"t","y"},
				PlotLabel->"(b) y = C(t/A)"];
Show[GraphicsArray[{{upper},{lower}}],
		PlotLabel->"Figure 23.6"]