task_sem3_1.5

#include <stdio.h>
#include <math.h>
#include "spline.h"

double t_2[2][2];
double t_3[3][2];
double t_4[4][2];
double t_5[5][2];
double t_6[6][2];
double t_spline_x[6];
double t_spline_y[6];
double t_spline_c[18];

double p(double x, double t[][2], int n) {
    double s = 0.0;

    for (int k = 0; k <= n; k++) {
        double m = t[k][1];
        for (int j = 0; j <= n; j++)
            if (j != k)
                m *= ((x - t[j][0]) / (t[k][0] - t[j][0]));
        s += m;
    }

    return s;
}

int main(int argc, char *argv[]) {
    double x = 23.0;

    /*** populate tables ***/

    // t_2
    t_2[0][0] = 20.0; t_2[0][1] = sin(t_2[0][0] * M_PI / 180.0);
    t_2[1][0] = 30.0; t_2[1][1] = sin(t_2[1][0] * M_PI / 180.0);

    // t_3
    for (int i = 0; i < 3; i++) {
        t_3[i][0] = 10.0 + 10.0 * i;
        t_3[i][1] = sin(t_3[i][0] * M_PI / 180.0);
    }

    // t_4
    for (int i = 0; i < 4; i++) {
        t_4[i][0] = 10.0 + 10.0 * i;
        t_4[i][1] = sin(t_4[i][0] * M_PI / 180.0);
    }

    // t_5
    for (int i = 0; i < 5; i++) {
        t_5[i][0] = 10.0 + 10.0 * i;
        t_5[i][1] = sin(t_5[i][0] * M_PI / 180.0);
    }

    // t_6
    for (int i = 0; i < 6; i++) {
        t_6[i][0] = 10.0 + 10.0 * i;
        t_6[i][1] = sin(t_6[i][0] * M_PI / 180.0);
    }

    // t_spline_x
    for (int i = 0; i < 6; i++) {
        t_spline_x[i] = 10.0 + 10.0 * i;
        t_spline_y[i] = sin(t_spline_x[i] * M_PI / 180);
    }

    /*** print result ***/

    printf("x = %.2lf\tsin(x) = %.9e\nP_1(x) = %.9e\tP_2(x) = %.9e\tP_3(x) = %.9e\tP_4(x) = %.9e\tP_5(x) = %.9e\t\nspline(x) = %.9e\n", x, sin(x * M_PI / 180), p(x, t_2, 1), p(x, t_3, 2), p(x, t_4, 3), p(x, t_5, 4), p(x, t_6, 5), seval(6, x, t_spline_x, t_spline_y, spline(6, t_spline_x, t_spline_y, t_spline_c)));

    return 0;
}