My program takes in a polynomial of any degree, and outputs it back the user. I want to be able to then pass this polynomial to a subfunction where it will be evaluated using the rectangular rule process. Currently i'm writing the function and I have run into a few problems, mainly having the correct coefficient be multiplied by the polynomial. I highlighted the parts of my program that deal with the rectangular rule.

Now for the rectangular rule, for instance if I had a function that was just x^2 to be integrated on the bounds of [0,1] with 2 subintervals, the change in x, or delta x, would be (1-0)/2, or right bound minus left bound divided by subintervals. So that means the total approximate area would be f(1/2)*deltax + f(1)*deltax, which can be simplified to [f(1/2) + f(1)] * deltax

I'm not sure if I need to pass the order through this function as well and decrease it as the for loops continues or not.Code:#include <stdio.h> #include <stdlib.h> int menu(void); void simpsonsrule(void); double rectanglerule(char *, double, double, double, int); main() { int j=1; //Loop for the menu int technique; //Integration technique int order; //Order for the polynomial int totterms; //Total number of terms in the equation double a; //left endpoint double b; //right endpoint double boundtotal; //endpoint math double subint; //subintervals int loopvar; //for loop variable double *ptr; int count; double rectarea; //Total area for the rectangle rule double simparea; //Total area for the simpson rule while(j) { puts("Welcome to the integration program."); puts("You can compute an integral using either Simpson's or the Rectangular rule."); puts("\nEnter the order of the polynomial you wish to integrate."); scanf("%d",&order); totterms= order+1; ptr=malloc(totterms*sizeof(double)); for(count=totterms-1;count >=0; count--) { if(count != 0) { printf("\nEnter the coefficient for the %d power: ", count); scanf("%lf", &ptr[count]); } else { printf("\nEnter the constant: "); scanf("%lf", &ptr[count]); } } puts("\nEnter the left endpoint of the integral."); scanf("%lf",&a); puts("\nEnter the right endpoint of the integral."); scanf("%lf",&b); puts("\nEnter the number of sub-intervals you want to use."); scanf("%lf",&subint); boundtotal= (b-a)/subint; printf("\nThe polynomial you entered was.\n"); for(loopvar=totterms-1;loopvar >=0;loopvar--) { if(loopvar != 0) { printf("%lf^%d + ",ptr[loopvar],loopvar); } else { printf("%lf.",ptr[loopvar],loopvar); } } printf("\nIt is going to be integrated from %lf to %lf.",a,b); printf("\nWith %lf subintervals.",subint); puts("\nTo integrate using Simpson's Rule enter 1."); puts("To integrate using the Rectangular Rule enter 2."); puts("To integrate using both techniques enter 3."); scanf("%d",&technique); if(technique == 1) { } else if(technique == 2) {rectarea=rectanglerule(ptr,a,b,subint,order);printf("The total area under the curve is %lf.", rectarea); } else if(technique == 3) { } else { puts("You did not enter a valid menu option, goodbye."); } j=menu(); } } int menu(void) { int j; puts("To restart the program enter 1."); puts("To quit the program enter 0."); scanf("%d",&j); return j; } void simpsonsrule(void) { }double rectanglerule(char *ptr, double a, double b, double subint, int order) { double approxarea=0; //Approximated total area int i; double deltax = (b-a)/subint; //Change in x throughout the entire x-axis double deltaxadd = (b-a)/subint; //Addition of the intervals to plug into functions for(i=subint;i>0;i--) { //approxarea+=(function expression); deltaxadd+=deltaxadd; }}

So far I have come up with...

This is giving me some errors though, saying chars cant be converted to doubles...Code:double rectanglerule(char *ptr, double a, double b, double subint, int order) { double approxarea=0; //Approximated total area int i; double deltax = (b-a)/subint; //Change in x throughout the entire x-axis double deltaxadd = (b-a)/subint; //Addition of the intervals to plug into functions double funcval=0; printf("Order of pol is %d", order); for(i=subint;i>0;i--) { for(order=order; order >= 0; order--) //order-1 because the constant can be added at the end { if(order !=0) { funcval+=(pow(&ptr[order], order)); } else { funcval+=(&ptr[order]); } } approxarea=funcval*deltax; approxarea+=approxarea; deltaxadd+=deltaxadd; } }