ZMIENIENIONE LAB3

#include <iostream>
#include <math.h>
#include <stdlib.h>
#include <cstdio>

using namespace std;

double funct_1(double x)
{
    return sin(x);
}

double funct_2(double x)
{
    return cos(x);
}

double funct_3(double x)
{
    return -sin(x);
}


int main(void)
{
    double a=0.0, b=18.0;
    int N=800;
    double h=(b-a)/(double)N;
    double pochodna_pierwsza,pochodna_druga;
    double x;
    double err1,err2;
    FILE *file1=fopen("pochodna_pierwsza.txt","w");
    FILE *file2=fopen("pochodna_druga.txt","w");
    fprintf(file1,"X: \t f = Cos(x): \t\t  Pochodna 1: \t\t Blad: \n");
    fprintf(file2,"X: \t f = Cos(x): \t\t  Pochodna 2: \t\t Blad: \n");

    for(int i=0;i<N;i++)
    {
        x=a+(double)i*h;
        pochodna_pierwsza=(-funct_1(x+2.0*h)+4.0*funct_1(x+h)-3.0*funct_1(x))/(2.0*h);
        err1=fabs(funct_2(x)-pochodna_pierwsza);
        fprintf(file1,"%.5lf\t%.15lf\t%.15lf\t%.15lf\n",x,funct_2(x),pochodna_pierwsza,err1);
        pochodna_druga=(funct_1(x+h)-2.0*funct_1(x)+funct_1(x-h))/(h*h);
        err2=fabs(funct_3(x)-pochodna_druga);
        fprintf(file2,"%.5lf\t%.15lf\t%.15lf\t%.15lf\n",x,funct_2(x),pochodna_druga,err2);
    }
    fclose(file1);
    fclose(file2);
    return 0;
}