mathematica画的螺旋线：

P1 = PolarPlot[thta, {thta, 0, Pi/2}];
P2 = PolarPlot[thta + Pi/2, {thta, -Pi/2, 0}];
P3 = PolarPlot[thta + Pi, {thta, -Pi, -Pi/2}];
P4 = PolarPlot[thta + Pi 3/2, {thta, -Pi 3/2, -Pi}];
Show[P1, P2, P3, P4]

P1 = PolarPlot[thta, {thta, 0, Pi}];
P2 = PolarPlot[thta + Pi/2, {thta, -Pi/2, Pi/2}];
P3 = PolarPlot[thta + Pi, {thta, -Pi, 0}];
P4 = PolarPlot[thta + Pi 3/2, {thta, -Pi 3/2, -Pi/2}];
Show[P1, P2, P3, P4]

P1 = PolarPlot[thta, {thta, 0, Pi/2}];
P3 = PolarPlot[thta + Pi, {thta, -Pi, -Pi/2}];
P2 = PolarPlot[Pi/2, {thta, 0, Pi 2}];
Show[P1, P2, P3]