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#include <iostream>
using namespace std ;
int main ()
{
int i = 1;
double arctan( double x );
double power( double x,int i );
cout << "The PI Is" << 16 * arctan( 0.2 ) - 4 * arctan( 1/239 ) << endl ;
system ( "pause" );
}
double power( double x, int i )
{
double n = 1 ;
while ( i > 0)
{
n = n * x;
i -- ;
}
return n ;
}
double arctan ( double x )
{
int j = 2;
int i = 1;
double result ;
while ( ( power( x,i ) / i) > 10E-15 )
{
result += (-1) * j * power( x, i ) * ( 1 / i ) ;
i = i + 2;
j++;
}
return result ;
}