Anonymous user
Roots of a function: Difference between revisions
Add C
(Add C) |
|||
Line 163:
Return ((x-3)*x+2)*x
}</lang>
=={{header|C}}==
Step & check until close, then use Secant method.
<lang c>#include <math.h>
#include <stdio.h>
double f(double x)
{
return x*x*x-3.0*x*x +2.0*x;
}
double secant( double xA, double xB, double(*f)(double) )
{
double e = 1.0e-12;
double fA, fB;
double d;
int i;
int limit = 50;
fA=(*f)(xA);
for (i=0; i<limit; i++) {
fB=(*f)(xB);
d = (xB - xA) / (fB - fA) * fB;
if (fabs(d) < e)
break;
xA = xB;
fA = fB;
xB -= d;
}
if (i==limit) {
printf("Function is not converging near (%7.4f,%7.4f).\n", xA,xB);
return -99.0;
}
return xB;
}
int main(int argc, char *argv[])
{
double step = 1.0e-2;
double e = 1.0e-12;
double x = -1.032; // just so we use secant method
double xx, value;
int s = (f(x)> 0.0);
while (x < 3.0) {
value = f(x);
if (fabs(value) < e) {
printf("Root found at x= %12.9f\n", x);
s = (f(x+.0001)>0.0);
}
else if ((value > 0.0) != s) {
xx = secant(x-step, x,&f);
printf("Root found at x= %12.9f\n", xx);
s = (f(x+.0001)>0.0);
}
x += step;
}
return 0;
}</lang>
=={{header|C++}}==
| |||