Hi. i wrote a script that finds the definite integral of a function using simpsons rule.(adsbygoogle = window.adsbygoogle || []).push({});

right now the function to be integrated is defined as 2*pow(9-pow(x,2),.5).

but this is very inconvenient to me because i must edit the program each time i want to find a new integral. my question is how do i define the function to be integrated inside the command prompt window? (in other words, i want the user to declare the function to be integrated, instead of the programmer declaring the function to be integrated.)

#include <stdio.h>

#include <math.h>

/*define f[x]*/

double f(double x)

{

double f=2*pow(9-pow(x,2),.5) ;

return f;

}

/*program main*/

int main()

{

double a,b,dx;

long double total1=0,total2=0;

long int n,i=1;

printf("b\nS f[x]dx\na\n\n");

printf("b=");

scanf("%lf",&b);

printf("a=");

scanf("%lf",&a);

printf("number of increments=");

scanf("%d",&n);

dx=(b-a)/n;

printf("%.13lf\n",dx);

/*calculations*/

while(i<=n-1)

{

total1=dx*f(a+i*dx)+total1;

printf("%d\r",i);

i=i+1;

}

i=0;

while(i<=n-1)

{

total2=dx*f(a+(i+.5)*dx)+total2;

printf("%d\r",i);

i=i+1;

}

double integral=total1/3+2*total2/3+dx*(f(a)+f(b))/6;

printf("definite integral=%.13lf", integral);

getchar();

getchar();

}

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# How do i declare a function in the command promp window (c++ question)

**Physics Forums | Science Articles, Homework Help, Discussion**