half division method. incorrectly calculates

I am writing a half-division method on C.

#include <stdio.h> #include <stdlib.h> #include <math.h> #define PI 3.14159 #define E 1e-5 #define A -5 #define B 2 double formula (double b) { double function_res = 2*b*b-9; //пока считаю по этой функции и все равно неправильно //pow(b, 3)* cos(3*PI*b)*exp(b)-pow(b,2)*cos(2*PI*b)*exp(0.5*b)+5; return function_res; } void halfDiv () { double* a = (double*)malloc(sizeof(double)); a[0] = A; double* b = (double*)malloc(sizeof(double)); b[0] = B; double* c = (double*)malloc(sizeof(double)); c[0] = (a[0] + b[0])/2; double* distance = (double*)malloc(sizeof(double)); distance[0] = abs(b[0]-a[0]); double* fa = (double*)malloc(sizeof(double)); fa[0] = formula(a[0]); double* fb = (double*)malloc(sizeof(double)); fb[0] = formula(b[0]); double* fc = (double*)malloc(sizeof(double)); fc[0] = formula(c[0]); int i = 0; printf("a\t\tb\t\tc\t\t|ba|\t\tf(a)\t\tf(b)\t\tf(c)\n%lf\t%lf\t%lf\t%lf\t%lf\t%lf\t%lf\n", a[0], b[0], c[0], distance[0], fa[0], fb[0], fc[0]); while (abs(distance[i] - E)*1e+5 > 10) { i++; a = (double*)realloc(a, (i +1)*sizeof(double)); b = (double*)realloc(b, (i +1)*sizeof(double)); c = (double*)realloc(c, (i +1)*sizeof(double)); distance = (double*)realloc(distance, (i +1)*sizeof(double)); fa = (double*)realloc(fa, (i +1)*sizeof(double)); fb = (double*)realloc(fb, (i +1)*sizeof(double)); fc = (double*)realloc(fc, (i +1)*sizeof(double)); a[i] = (fc[i - 1]<0) ? c[i - 1] : a[i - 1]; b[i] = (fc[i-1]>0) ? c[i-1] : b[i-1]; c[i] = (a[i]+b[i])/2; distance[i] = abs(b[i]-a[i]); fa[i] = formula(a[i]); fb[i] = formula(b[i]); fc[i] = formula(c[i]); printf("%lf\t%lf\t%lf\t%lf\t%lf\t%lf\t%lf\n", a[i], b[i], c[i], distance[i], fa[i], fb[i], fc[i]); } double x = c[sizeof(c)/sizeof(c[0])-1]; double fx = formula(x); printf("\n\nx = %lf\nf(x) = %lf"); return; } int main() { halfDiv(); return 0; } 

here is the code. but for some reason he thinks everything is wrong. Neither the function is wrong, nor even the distance, which the program calculates in general it is not clear which side All seems to be in the same data type. Tell me, please, what's the problem.