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#include <stdio.h> | |
#include <math.h> | |
const double ROOT3 = 1.73205080756887729352744634150587236694280525381; | |
double f(double x) { | |
return (x*x - 3); | |
} | |
double df(double x) { | |
return (2 * x); | |
} | |
int swap(double *a, double *b) { | |
int tmp = *a; | |
*a = *b; | |
*b = tmp; | |
return 0; | |
} | |
//Usage: newton(ค่าเริ่มต้น, จำนวนครั้ง, ฟังชั้น, อนุพันธ์พังชั้น); | |
//Return: ตำแหน่ง x ใกล้ 0 | |
double newton(double start, int n, double fc(double x), double dfc(double x)) { | |
double x = start, error; | |
int sign; | |
if (fc(start) > 0.0) { | |
sign = -1; | |
} | |
else { | |
sign = 1; | |
} | |
for (int i = 0; i <= n; i++){ | |
x = x + (fc(x) / dfc(x))*sign; | |
error = ROOT3 - x; | |
printf("x = %.16f\n", x); | |
printf("log|error| = %.16f\n", log10(fabs(error))); | |
} | |
return x; | |
} | |
//Usage: newton(ค่าด้านซ้าย, ค่าด้านขวา, จำนวนครั้ง, ฟังชั้น); | |
//Return: ตำแหน่ง x ใกล้ 0 | |
double bisection(double a, double b, int n, double fc(double x)) { | |
double check, error; | |
if (a > b) { | |
swap(&a, &b); | |
} | |
for (int i = 0; i <= n; i++) { | |
check = (a + b) / 2; | |
if (fc(check) >= 0) { | |
b = check; | |
} | |
else { | |
a = check; | |
} | |
error = ROOT3 - check; | |
printf("x = %.16f\n", check); | |
printf("log|error| = %.16f\n", log10(fabs(error))); | |
} | |
return check; | |
} | |
int main(int argc, char *argv []) { | |
printf("Newton Method Test\n"); | |
newton(3.0, 10, f, df); | |
printf("\nbisection Method Test\n"); | |
bisection(1.0, 3.0, 10, f); | |
return 0; | |
} |
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