Summary
We have seen that given a positive valued function on an interval
[a,b], the area under the curve on that interval can be approximated
by:
A≈n∑i=1f(xi∗)Δx
where xi∗ is any x value in the ith interval and Δx
is the length of each rectangle.
And we have seen that the larger the value of n, the better the
approximations.
We are ready to define the area under this curve:
A=limn→∞n∑i=1f(xi)Δx
This limit is so important that we give it a special name and notation.
It is the integral of f(x) from a to b, and is denoted
∫baf(x)dx.
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