interpolation

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

double f(double x) {
    return sin(x) / x;
}
double L(double *x, int n, double a) {
    double rez = 0, l;
    int i, j;
    for (i = 0; i < n; i++) {
        l = 1;
        for (j = 0; j < n; j++) {
            if (i != j) {
                l = l * (a - x[j]);
                l = l / (x[i] - x[j]);
            }
        }
        rez = rez + f(x[i]) * l;
    }
    return rez;
}

int main() {
    double *x, tochka;
    int n;
    printf("enter n (kolichestvo peremennih v kotorih izvestno znachenie): ");
    scanf("%d", &n);
    x = (double*)malloc(sizeof(double) * n);
    if (x == NULL) {
        printf("malloc x error\n");
        return -1;
    }
    for (int i = 0; i < n; i++) {
        printf("%d\nenter xi :", i);
        scanf("%lf", &x[i]);
    }
    printf("enter x v kotorom hotim y: ");
    scanf("%lf", &tochka);
    printf("lagranj: %lf\n", L(x, n, tochka));
    printf("the real value in tochka: %lf\n", f(tochka));
    free(x);
    return 0;
}