definite integral

given a function that is continuous on the interval , we divide the interval into subintervals of equal width, , and from each interval choose a point, . then the definite integral of from to is:
in practicality:



the casio calculator with a model name containing 991 can calculate definite integrals

but ofcourse if you're doing homework or you're just doing math in a non-restricting environment you can use sagemath
integral(sin(x)^3 + sin(x), x, 0, pi)
10/3

this is our first exercise dealing with integration of a function containing , we use integration by parts
we use the same method to find the integral on the right
then we substitute the result of the integral in the original equation