Contour Plot -- Not Displaying
because one has to deliver variables in the plot functions which relate to the variables given in the domain specification of the plot. For all explicit plot functions the variables must be the same, so
Clear[h, h1]
h[x_, y_, w_] := Cos[2 \[Pi] (x^2 + y^2)/(2 5 w)]^2
h1[x_, y_] := h[x, y, 17.]
then still you don't see an output with
ContourPlot[h1[x, y]==1, {x, -15, 15}, {y, -15, 15},GridLines -> Automatic]
despite
In[54]:= FindInstance[1/170 (x^2 + y^2) == 1, {x, y}, Reals, 3] // N
Out[54]= {{x -> 9.5, y -> 8.93029}, {x -> -10.3333, y -> -7.95124}, {x -> 3.25, y -> 12.6269}}
the request has a meaningful domain. If you mouse over
ContourPlot[h1[x, y], {x, -15, 15}, {y, -15, 15}, Contours -> 10]
you see value 1 is not caught. In the manual ContourPlot is a hint
Contours for functions f(x,y) = 0 where f(x,y) >= 0 are always poorly detected
This is the case here (for h1[x,y]==1 where h1[x,y]<=1).
This works
Plot3D[h1[x, y], {x, -15, 15}, {y, -15, 15}, PlotPoints -> {31, 39}]