## Question

**groeneveldd52** on *Thu, 04 Feb 2016 07:22:53 *

So I'm writing a code to solve for the two angles and missing side of a right triangle. The code has no errors and solves for my side ("c") perfectly. However for the angles it prints out -nan(ind). I have been in this class for a total of maybe 5 class meetings so i don't know what is going on or how to fix it. So if anyone can plainly explain the issue as though i have no clue what any of the C++ terminology actually is. lol! thank you. Any help is great otherwise just don't.

Here is the code:

#include <iostream>;#include <cmath>;

using namespace std;

int main()

{

long double a, b, c, A, A1, B1, B, tot1, tot2, tot3;

char done, an;

cout << "input value of a \n";

cin >> a;

cout << "input value of b \n";

cin >> b;

tot1 = a*a + b*b;

c = sqrt(tot1);

cout << "c=" << c <<"\n";

tot2 = (b*b + c*c - a*a) / 2 * b*c;

A1 = acos(tot2);

A = A1 * 180 / 3.14;

cout << A << "\n";

cin >> done;

tot3 = (a*a + c*c - b*b) / 2 * a*c;

B1 = acos(tot3);

B = B1 * 180 / 3.14;

cout << B << "\n";

cin >> done;

cout << "C is equal to 90 degrees \n ";

system("pause");

return 0;

};

## Replies

**Barry-Schwarz** on *Thu, 04 Feb 2016 08:32:13 *

tot2 = (b*b + c*c - a*a) / 2 * b*c;Your formula for tot2 is incorrect. You are missing a set of parentheses around the divisor.

A1 = acos(tot2);

**Hart Wang** on *Thu, 04 Feb 2016 09:04:27 *

Hi,

I had test the code, we can reproduce the issue. In order to solve issue. you should do it ：

tot2 = ((b*b + c*c - a*a) /( 2 * b*c))；

Best Regards,

Hart

**Pavel A** on *Thu, 04 Feb 2016 16:07:15 *

This "NAN" thing means "Not A Number". Unlike integer numbers, where every combination of bits is some valid value - floating numbers have more complex structure (pardon the pun) and some combination of bits do not represent a valid floating point value. The c++ library knows to detect such things.

The "ind" after "nan" means some specific flavor of "non-numberness". So you either are trying to print an uninitialized variable, or a result of invalid operation.

-- pa