Function Command

Function[Function f, Number a, Number b]

Yields a function graph, that is equal to f on the interval [a, b] and not defined outside of [a, b].

Note:

• This command should be used only to restrict the display interval of a function. To restrict the function’s domain, create a conditional function with the If command, e.g.
  f(x) = If[-1 < x && x < 1, x²].
• Example: f(x) = Function[x^2, -1, 1] produces a function equal to x² whose graph appears only in the interval [-1, 1]. However, while g(x) = 2 f(x) will produce the function g(x) = 2 x² as expected, this function is not restricted to the interval [-1, 1].