#include <stdio.h>
#include <stdlib.h>
#include <math.h>


int main(void){
    double dx = 0, dy = 0, dAO = 0, dAU = 0, dAT = 0, dxmin = 0, dxmax = 0, dXAbst = 0, dxph = 0, dyxph = 0, dAres = 0; /*dx: x-wert, dy: zugehöriger y-wert, dAO: Fläche Obersumme, dAU: Fläche Untersumme, dxmin: Untere Grenze,*/
    int iSpAnz = 0, iGelesen = 0, i = 0; /*SpaltenAnzahl*/
    fprintf(stderr, "Numerische Integration\n\nf(x)=x^2+2x+3\n\n");
    fprintf(stderr, "Untere Grenze:\t", dxmin);
    scanf("%lf", &dxmin);
    fprintf(stderr, "Obere Grenze:\t", dxmax);
    scanf("%lf", &dxmax);
    fprintf(stderr, "Spaltenanzahl:\t", iSpAnz);
    scanf("%d", &iSpAnz);
    /*do {
        iGelesen = scanf("%lf;%lf;%d", &dxmin, &dxmax, &iSpAnz);
        while(getchar()!='\n');
    } while(iGelesen != 3);
    */
    dXAbst = (dxmax - dxmin) / iSpAnz;
    for (i = 1; i <= iSpAnz; i = i + 1){
        dx = dxmin + dXAbst * i;
        dy = fabs(dx*dx + 2*dx + 3);
        dAO = dAO + dy * dXAbst;}
    for (i = 0; i < iSpAnz; i = i + 1){
        dx = dxmin + dXAbst * i;
        dy = fabs(dx*dx + 2*dx + 3);
        dAU = dAU + dy * dXAbst;}
    for (i = 0; i < iSpAnz; i = i + 1){
        dx = dxmin + dXAbst * i;
        dxph = fabs(dxmin + dXAbst * (i + 1));
        dy = fabs(dx*dx + 2*dx + 3);
        dyxph = dxph*dxph + 2*dxph + 3;
        dAT = dAT + (0.5 * dXAbst * (dy + dyxph));}
	iSpAnz = 10000;
    for (i = 0; i < iSpAnz; i = i + 1){
        dx = dxmin + dXAbst * i;
        dxph = fabs(dxmin + dXAbst * (i + 1));
        dy = fabs(dx*dx + 2*dx + 3);
        dyxph = dxph*dxph + 2*dxph + 3;
        dAres = dAres + (0.5 * dXAbst * (dy + dyxph));}


    fprintf(stderr, "Obersumme: %.2f\nUntersumme: %.2f\nTrapezregel: %.2f\nGenaue Flaeche (n=10000): %.2f\n", dAO, dAU, dAT, dAres);


  system("PAUSE");
  return 0;
}