I am new to programming and am taking edX's CS50 (Intro to Programming) class. There is this C code that I have been trying to compile, but always results in an error message that looks like this:
[![error message](https://i.stack.imgur.com/Kxeqw.png)](https://i.stack.imgur.com/Kxeqw.png)

This is the code lines that I have been trying to compile:

```
#include <cs50.h>
#include <stdio.h>
#include <math.h>

int main (void)
{
   bool valid_triangle (float a, float b, float c);
   bool valid_triangle (float a, float b, float c)
  {
   // check positive values
     if ( a <= 0 || b <= 0 || c <= 0 )
    {
    return false;
     }
    //check two sides are longer
    if ( (a + b <= c) || (a+c <= b) || (b+c <= a))
    {
    return false;
    }

    //otherwise return true
     return true;
 }

}

```

Does anyone know what I did wrong and how to fix this error? Thanks a lot!