I would, but the code I am using is a Particle Swarm Optimization that prints the graph out after every iteration.  The x^n thing was just an example so I would not have to copy all of the code in here.

Try

plot(cos(20*Pi*t), t = -5..5, numpoints=500)

This will increase the number of points that Maple will put on the graph.  The bigger the number the more points, but the longer calculation time.

Hatfield