ClearAll;
tcirc1 = 2.35; tcirc2 = tcirc1 + Pi/2; tcirc3 = tcirc1 + Pi; tcirc0 = tcirc1 - Pi/2;
plotsin = Plot[Sin[t],{t,0,6 Pi},PlotPoints->100,
				PlotRange->{{0,6 Pi},{-1.01,1.01}},
				AxesOrigin->{-0.5,-1.1},
				Ticks->{{0,{3Pi,FontForm["3p",{"Symbol",9}]},{6Pi,FontForm["6p",{"Symbol",9}]},{tcirc2,FontForm["q+p/2",{"Symbol",9}]}},{{-1,"-1"},{0,"0"},{1,"1"}}},
				AxesLabel->{"t","y"},
				PlotLabel->"(a) y = S(t)"];
plotcos = Plot[Cos[t],{t,0,6 Pi},PlotPoints->100,
				PlotRange->{{0,6 Pi},{-1.01,1.01}},
				AxesOrigin->{-0.5,-1.1},
				Ticks->{{0,{3Pi,FontForm["3p",{"Symbol",9}]},{6Pi,FontForm["6p",{"Symbol",9}]},{tcirc1,FontForm["q",{"Symbol",9}]},{tcirc3,FontForm["q+p",{"Symbol",9}]}},{{-1,"-1"},{0,"0"},{1,"1"}}},
				AxesLabel->{"t","y"},
				PlotLabel->"(b) y = C(t)"];
plotnegcos = Plot[-Cos[t],{t,0,6 Pi},PlotPoints->100,PlotStyle->Dashing[{0.01,0.01}]];
plotnegsin = Plot[-Sin[t],{t,0,6 Pi},PlotPoints->100,PlotStyle->Dashing[{0.01,0.01}]];
zeroline = Graphics[{Dashing[{0.001,0.01}],Line[{{0,0},{6Pi,0}}]}];
circc1 = Graphics[Disk[{tcirc1,Cos[tcirc1]},{0.2,0.04}]];
circc2 = Graphics[Disk[{tcirc3,-Cos[tcirc3]},{0.2,0.04}]];
circs2 = Graphics[Disk[{tcirc2,Sin[tcirc2]},{0.2,0.04}]];
circs1 = Graphics[{{GrayLevel[1.0],Disk[{tcirc1,Sin[tcirc1]},{0.2,0.04}]},Circle[{tcirc1,Sin[tcirc1]},{0.2,0.04}]}];
circs3 = Graphics[{{GrayLevel[1.0],Disk[{tcirc3,-Sin[tcirc3]},{0.2,0.04}]},Circle[{tcirc3,-Sin[tcirc3]},{0.2,0.04}]}];
circc0 = Graphics[{{GrayLevel[1.0],Disk[{tcirc0,Cos[tcirc0]},{0.2,0.04}]},Circle[{tcirc0,Cos[tcirc0]},{0.2,0.04}]}];
Show[GraphicsArray[{{Show[plotsin,plotnegsin,zeroline,circs1,circs2,circs3]},
	                {Show[plotcos,plotnegcos,zeroline,circc0,circc1,circc2]}},
		PlotLabel->"Figure 23.4"]]