Question: wave function ploting

I want to make a plot of this function sine and imaginary cosine below,

psi(x):=sin(k*x)+I*k*l[2]*cos(k*x);

where

k:=n*pi/L;
 
L=1,n=1,l[2]=1;

plot(psi(x),x=0..5);

Plotting error, empty plot.

i always recieve this Error. Can someone help me with this. You can take any range of x including Pi if you wish , and as well provide me with refrences Text book on ploting functions if He/She knows. Looking forward for feedbacks. Thank you very much .
      
                                           

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