exp

    double exp(double);

calculates the exponential value of a number

#include <iostream> /* including standard library */
#include <cmath> /* including math library */
 
using namespace std;
int main ( void ) 
{
    double x;
    x = 9.0;
 
    //cout.setf(ios::fixed, ios::floatfield);
    cout.precision(8);
 
    cout << "the exponential value of " << x << " is " << exp(x) << endl;
    return 0;
}

 output:
 the exponential value of 9.0 is 8103.0839