Plotting

plot(sin(x), x = -2*Pi..2*Pi);

plot takes an expression and a range for the variable. For more than one curve on the same axes:

plot([sin(x), cos(x)], x = -2*Pi..2*Pi);

Why This Matters for Your Exams

Seeing a function's actual shape makes it much easier to sanity-check an answer you got symbolically — if your computed maximum doesn't match where the plot peaks, you've likely made an algebra mistake somewhere.