Question: Maple 18 can't plot

Hi everyone, I got a problem. I'm a new user and I'm getting to know this beautiful software.

The problem is that when I enter a function in math mode (the easyest with simple inputs I guess), once I right click and plot only the cartesian plot is shown, without the actual function. 

What should I try? Math without plots is boring... :)

 

Thank you!

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