' - - File:XII_Contour1a.txt

F{x,y} =cos[x] + cos[y]

r = 12   ' Use a square box.

' Optional: Add axes.
Ux<t> = <t,0,0> : Uy<t> = <0,t,0>  :  Uz<t> = <0,0,t>
Plot[Ux,Uy,Uz,{t,-r,r,100}]

'  Level = -5, 0, +5, with starting coordinate (4,4), & DEFAUT: error = 0.1; segment = 0.2

PlotContour[F,{-r,r,-r,r}{4,4}{0.5, 1, 2}]

PlotContour[F,{-r,r,-r,r}{2,2}{0.5, 1, 2}]


