The Fundamental Theorem of Calculus, Part II goes like this: Suppose `F(x)` is an antiderivative
of `f(x)`. Then
[`int_a^b f(x) dx = F(b) - F(a).`]
This might be considered the "practical" part of the FTC, because it allows us to
actually compute the area between the graph and the `x`-axis.
In this exploration we'll try to see why FTC part II is true.
Drag the blue points `a` and `b` to make things happen.