evaluates the definite integral using Simpson's 1/3rd Method
integral = simpson(a,b,n,f)
lower limit of integration
upper limit of integration
an even no. (denotes the no. of sub-intervals. Higher the value of n better the result.)
The function that is to be integrated
returns the definite integral using Simpson's 1/3rd Method
http://www.phy.davidson.edu/FacHome/dmb/py200/Simpson.htm
http://www.bragitoff.com/2016/02/simpsons-13rd-rule-integration-scilab-codeprogrammacro/