Hello I´m trying to plot the fowllowing function using maple without success: f:=t->sum(Dirac(t-k*pi),k=1..20); it seems to be syntax right. Then when I try to plot it using plot (f(t),t=-10..10); I do get an error message: 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 Error, empty plot What is happening?