The good-looking function will show such expressions by using exponents; for illustration,
>> b = sym('x^2')
There are many plot functions in a MATLAB with names starting with "ez" which perform the essential conversions from symbolic expressions to numbers and plot them. For illustration, the function ezplot will draw a 2-D plot in the x-range from -2π to 2π, with the expression as the title. The expression
>> ezplot('x^3 + 3*x^2 - 2')
generates the figure as shown in figure.
The domain for the ezplot function can also be identified; for illustration, to change the x-axis to be from 0 to π, it is identified as a vector. The result is as shown in figure.
>> ezplot('cos(x)',[0 pi])