C++ power function with variables

Question

#include <cstdlib>
#include <iostream>
#include <cmath>
using namespace std;

int main(int argc, char *argv[])
{
    double amount, rate, time, interest, month;
    interest = rate/(12.0*100);
    month = (amount * rate)/1.0 -(1.0 + interest), pow(time*12);
    cout << "What is the amount of the loan? $ ";
    cin >> amount;
    cout << "What is the annual percentage rate? ";
    cin >> rate;
    cout << "How many years will you take to pay back the loan?  ";
    cin >> time;
    cout <<"\n-------------------------------------------------------\n";
    cout << "Amount        Annual % Interest       Years         Monthly Payment\n\n\n";
    cout <<amount <<"                      " <<rate <<"               " <<time << "        " <<month;
    cout <<"\n\n";
    system("PAUSE");
    return EXIT_SUCCESS;
}

I am getting an error here and am not sure exactly how to use the pow function properly. The formula according to the problem is:

 Monthly payment = (loan amount)(monthly interest rate) / 1.0 - (1.0 + Monthly interest rate)^-(number of months)

Here is the line that I am having trouble with

month = (amount * rate)/1.0 -(1.0 + interest), pow(time*12);

Thanks for the help

Answer 1

std::pow accepts two arguments like so

pow (7.0,3) 

So your code should be more like this

month = (amount * rate)/1.0 - std::pow( (1.0 + interest), 12);

Your code has other flaws as well, like you do calculation before you set the values.