The area
command approximates the area under a graph.
area takes four arguments:
expr, an expression f(x).
var=a..b, the variable with a range.
n, a positive integer.
method, the approximation method to use, which can
be one of:
trapezoid
left_rectangle
right_rectangle
middle_point
simpson
rombergt
(Romberg with the trapezoid method)
rombergm
(Romberg with the midpoint method)
gauss15
(The 15 point Gaussian quadrature)
area(expr,var=a..b,n,method)
returns an approximation to the area under the graph over the given
interval, using the specified method with n subdivisions (or 2n
subdivisions for rombergt, rombergm and
gauss15).