This may be a very easy question to answer. But I can't get maple to plot a function. What I need is a 3D plot of: v2 vs epsilon vs r With the variable k varying between 1 and 2, and r varying between 1 and 250. but every time I try to plot, the program gives an error "Warning, unable to evaluate the function to numeric values in the region; see the plotting command's help page to ensure the calling sequence is correct". But if you manually calculate v2 and epsilon using the values given, they wrk out fine. I'm sure I'm just not doing something right but I can't seem to figure out what.