In this lab we will graph functions of more than one variable.

F1[x_,y_] =x^2+y^2
Plot3D[F1[x,y],{x,-3,3},{y,-3,3},BoxRatios->{1,1,1}]

Use this idea to plot F2[x_,y_] = x^-y^2.

F1[x_,y_] =x^2+y^2
Plot3D[F1[x,y],{x,-3,3},{y,-3,3},BoxRatios->{1,1,1}]

ParametricPlot3D[{(3+Cos[t]) Sin[s],(3+Cos[t]) Cos[s],Sin[t]},{s,0,2Pi},{t,0,2Pi},PlotStyle->{Green}]

This torus has inner radius 4 and outer radius 6 (i.e. the circle is of radius 1 centered at radial distance 5. Use this idea to plot  a torus with inner radius 1 and outer radius 3.
Note that there are 3 parts ... { x(t,s),  y(t,s),  z(t,s) }

ParametricPlot3D[{(3+Cos[t]) Sin[s],(3+Cos[t]) Cos[s],Sin[t]},{s,0,2Pi},{t,0,2Pi},PlotStyle->{Red}]

This torus has inner radius 3 and outer radius 8 (i.e. the circle is of radius 2.5 centered at radial distance 5.5. Use this idea to plot  a torus with inner radius 1 and outer radius 3.
     Note that there are 3 parts ... { x (t, s),  y (t, s),  z (t, s) }

ParametricPlot3D[{(5+Cos[t]) Sin[s],(5+Cos[t]) Cos[s],Sin[t]},{s,0,2Pi},{t,0,2Pi},PlotStyle->{Blue}]

Attempt to give a parametric plot of the unit sphere

ParametricPlot3D[{(5+Cos[t]) Sin[s],(5+Cos[t]) Cos[s],Sin[t]},{s,0,2Pi},{t,0,2Pi},PlotStyle->{Blue}]