Author 
Comment/Response 
yehuda

02/27/13 02:53am
note  your function is not defined for x,y=0
for the first question where the ContourPlot generates an empty graph you need to change the line to
ContourPlot[f[x, y] == 1, {x, 30 Pi, 30 Pi}, {y, 45 Pi, 20 Pi},
Axes > True]
(* i.e., include the argument x,y in the call to f *)
for the second question, you need to use graphics primitives yourself and actually repeat what PlotLegend does. This is a task too large to answer as a forum question
yehuda
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