I redid the code again but this time I get an error c2061 identifier 'cout'. Someone explain to me this. I am pretty new with C++ I highly appreciate it.

```
#include <iostream>
#include <cmath>
using namespace std;
const double pi = 3.14159265;
int main ()
{
string name;
string homework;
name = "Randy Calhoun, Giannis Combe, Jonathan Vega";
homework = "Project 1";
cout << "Randy Calhoun, Giannis Combe, Jonathan Vega" << endl;
cout << "Project 1" << endl;
int index;
double input1, input2, output;
bool quit, back, back2;
do
cout << "0. Quit\n";
cout << "1. Unit Conversions\n";
cout << "2. Math Operations\n";
cout << "3. Math Functions\n";
quit = false;
cin >> index;
switch(index)
{
case 0:
quit = true;
break;
case 1:
cout << " 0. Back to Previous Menu\n";
cout << " 1. From Inches to Meters\n";
cout << " 2. From Meters to Inches\n";
cout << " 3. From Kilograms to Pounds\n";
cout << " 4. From Pounds to Kilograms\n";
cout << " 5. From km/hr to mi/hr\n";
cout << " 6. From mi/hr to ki/hr\n";
cout << " 7. From Newtons to lbf\n";
cout << " 8. From lbf to Newtons\n";
cout << " 9. From Pa to PSI\n";
cout << " 10. From PSI to Pa\n";
back = false;
cin >> index;
switch (index)
{
case 0:
back = true;
break;
case 1:
cout << "Convert inches to meters:\n";
cin >> input1;
output = input1 * 25.4/1000;
cout << "It equals " << output << "m\n";
break;
case 2:
cout << "Convert meters to inches:\n";
cin >> input2;
output = input2 * 1000/25.4;
cout << "It equals " << output << "m\n";
break;
case 3:
cout << "Convert kilograms to pounds:\n";
cin >> input1;
output = input1 * 2.2;
cout << "It equals " << output << "m\n";
break;
case 4:
cout << "Convert Pounds to Kilograms:\n";
cin >> input2;
output = input2 / 2.2;
cout << "It equals " << output << "m\n";
break;
case 5:
cout << "Convert km/hr to mi/hr:\n";
cin >> input1;
output = input1 / 1.609344;
cout << "It equals " << output << "m\n";
break;
case 6:
cout << "Convert mi/hr to km/hr:\n";
cin >> input2;
output = input2 / 1.609344;
cout << "It equals " << output << "m\n";
break;
case 7:
cout << "Convert Newtons to lbf:\n";
cin >> input1;
output = input1 / 4.44822;
cout << "It equals " << output << "m\n";
break;
case 8:
cout << "Convert lbf to Newtons:\n";
cin >> input2;
output = input2 * 4.44822;
cout << "It equals " << output << "m\n";
break;
case 9:
cout << "Convert Pa to PSI:\n";
cin >> input1;
output = input1 / 6,894.75729;
cout << "It equals " << output << "m\n";
break;
case 10:
cout << "Convert PSI to Pa:\n";
cin >> input2;
output = input2 * 6,894.75729;
cout << "It equals " << output << "m\n";
break;
default:
cout << "Enter an option\n";
break;
}while (back != true);
break;
case 2:
int index, c, b, a;
do
{
cout << " 0. Back to Previous Menu\n";
cout << " 1. Calculations for +\n";
cout << " 2. Calculations for -\n";
cout << " 3. Calculations for *\n";
cout << " 4. Calculations for /\n";
cout << " 5. Calculations for %\n";
back = false;
cin >> index;
switch (index)
{
case 0:
back = true;
break;
case 1:
cout << "How to calculate addition\n";
cout << "Enter a number for a and b\n";
c = a + b;
cout << "The result is" << c << "\n";
break;
case 2:
cout << "How to calculate subtraction\n";
cout << "Enter a number for a and b\n";
c = a - b;
cout << "The result is" << c << "\n";
break;
case 3:
cout << "How to calculate multiplication \n";
cout << "Enter a number\n";
c = a * b;
cout << "The result is" << c << "\n";
break;
case 4:
cout << "How to calculate division\n";
cout << "Enter a number\n";
c = a / b;
cout << "The result is" << c << "\n";
break;
case 5:
cout << "How to calculate Remainder\n";
cout << "Enter a number\n";
c = a % b;
cout << "The result is" << c << "\n";
break;
}
}while(back != true);
break;
case 3:
int i;
double n, x, y, result;
cout << " 0. Back to Previous Menu\n";
cout << " 1. Calculations for Absolute Value\n";
cout << " 2. Calculations for Square Root\n";
cout << " 3. Calculations for powers\n";
cout << " 4. Calculations for exponential\n";
cout << " 5. Calculations for Logarithms\n";
cout << " 6. Calculations for Log base ten\n";
cout << " 7. Calculations for Sine\n";
cout << " 8. Calculations for Cosine\n";
cout << " 9. Calculations for Tangent\n";
cout << " 10. Calculations for Arcsine\n";
cout << " 11. Calculations for Arccosine\n";
cout << " 12. Calculations for Arctangent\n";
cout << " 13. Calculations for Arctangent2\n";
cout << " 14. Calculations for Sinh\n";
cout << " 15. Calculations for Cosh\n";
cout << " 16. Calculations for Tanh\n";
cout << " 17. Calculations for Ceil\n";
cout << " 18. Calculations for Floor\n";
do
{
cin >> i;
switch(i)
{
case 0:
back = true;
break;
case 1:
cout << "Calculations for Absolute value\n";
cout << " Enter a number\n";
result = fabs(n);
cout << "The result is" << result << "\n";
break;
case 2:
cout << "Calculations for Square Roots\n";
cout << "Enter a number\n";
result = sqrt(n);
cout << "The result is" << result << "\n";
break;
case 3:
cout << "Calculations for powers\n";
cout << "Enter a number\n";
result = pow(n,x);
cout << "The result is" << result << "\n";
break;
case 4:
cout << "Calculations for exponential\n";
cout << "Enter an exponential value\n";
result = exp(n);
cout << "The result is" << result << "\n";
break;
case 5:
cout << "Calculations for Logarithms\n";
cout << "Enter a number\n";
result = log(n);
cout << "The result is" << result << "\n";
break;
case 6:
cout << "Calculations for Log base ten\n";
cout << "Enter a number\n";
result = log10(n);
cout << "The result is" << result << "\n";
break;
case 7:
cout << "Calculations for Sin\n";
cout << "Enter a number\n";
result = sin (n * pi / 180);
cout << "The result is" << result << "\n";
break;
case 8:
cout << "Calculations for Cosine\n";
cout << "Enter a number\n";
result = cos (n * pi / 180);
cout << "The result is" << result << "\n";
break;
case 9:
cout << "Calculations for Tangent\n";
cout << "Enter a number\n";
result = tan(n * pi / 180);
cout << "The result is" << result << "\n";
break;
case 10:
cout << "Calculations for Arcsine\n";
cout << "Enter a number\n";
result = asin(n) * 180.0 / pi;
cout << "The result is" << result << "\n";
break;
case 11:
cout << "Calculations for Arccosine\n";
cout << "Enter a number\n";
result = acos(n) * 180.0 / pi;
cout << "The result is" << result << "\n";
break;
case 12:
cout << "Calculations for Arctangent\n";
cout << "Enter a number\n";
result = atan(n) * 180.0 / pi;
cout << "The result is" << result << "\n";
break;
case 13:
cout << "Calculations for Arctangent2\n";
cout << "Enter a number\n";
result = exp(n);
cout << "The result is" << result << "\n";
break;
case 14:
cout << "Calculations for Sinh\n";
cout << "Enter a number\n";
result = sinh(n);
cout << "The result is" << result << "\n";
break;
case 15:
cout << "Calculations for Cosh\n";
cout << "Enter a number\n";
result = cosh(n);
cout << "The result is" << result << "\n";
break;
case 16:
cout << "Calculations for tanh\n";
cout << "Enter a number\n";
result = tanh(n);
cout << "The result is" << result << "\n";
break;
case 17:
cout << "Calculations for ceil\n";
cout << "ceil of a number is\n" << n;
break;
case 18:
cout << "Calculations for floor\n";
cout << "floor of a number is\n" << n;
break;
break;
default:
cout << "Enter any of the options\n";
break;
}
}while (quit != true);
system ("pause");
return 0;
}
}
```