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Definite integral

67 bytes added, 21:23, December 30, 2008
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==Definite Integrals==
 
 
A definite integral is the area under the curve between two points on the function. In the picture below, the yellow area is "positive" and the blue area is "negative". The integral is evaluated by adding the positive area together and subtracting the negative area.
If the function f(x) is real rather than complex, then the definite integral is also known as a Riemann integral.
 
 
== Solving Definite Integrals ==
Solving a definite integral usually has two main steps: [[integration]] and [[subtraction]].
 
 
== Example 1==
: <math>F(5) = {1 \over 3}5^3 = {125 \over 3}</math>
: <math>F(-3) = {1 \over 3}(-3)^3 = {-27 \over 3}</math>
<br />And subtract:
: <math>{125 \over 3} - {-27 \over 3} = {125 \over 3} + {27 \over 3} </math>
: <math>= {152 \over 3}</math>
: <math>\int_4^{12}\frac{3x+11}{x^2-x-6}dx </math>
=== Integration ===
<br />See the [[Partial fractions in integration]] page for how to integratethe above expression (it is the example).
<br />As shown on the page mentioned above:
: <math>\int\frac{3x+11}{x^2-x-6}dx=4ln|x-3|-ln|x+2|+c</math>
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