For the plot commmand, the functions f(x), f(t), g(t) can use any
valid JavaScript function or constant (without the "Math." prefix) and any
of the following:
+, -, *, /, ^, pi, e, sqrt(), ln(), abs(), sign(), floor(), ceil(),
n!, C(n,k), ran(a,b,n),
sin(), cos(), tan(), sin^-1(), cos^-1(), tan^-1(),
sinh(), cosh(), tanh(), sinh^-1(), cosh^-1(), tanh^-1(),
sech(), csch(), coth(), sech^-1(), csch^-1(), coth^-1().
cpi and ctheta denote the corresponding greek letters.
The multiplication symbol * can be omitted after a digit (0-9)
or a closing parenthesis.
