# 1.4 Utility Functions (Easy)

### Create rtweekend.h

Create rtweekend.h under the src directory

```cpp
#ifndef RTWEEKEND_H
#define RTWEEKEND_H

#include <cmath>
#include <iostream>
#include <limits>
#include <memory>


// C++ Std Usings

using std::make_shared;
using std::shared_ptr;

// Constants

const double infinity = std::numeric_limits<double>::infinity();
const double pi = 3.1415926535897932385;

// Utility Functions

inline double degrees_to_radians(double degrees) {
    return degrees * pi / 180.0;
}

// Common Headers

#include "color.h"
#include "ray.h"
#include "vec3.h"

#endif
```

### Make Revision to Following Files

#### hittable\_list.h

```cpp
#include "hittable.h"

//#include <memory>
#include <vector>

//using std::make_shared;
//using std::shared_ptr;
```

#### hittable.h

```cpp
//#include "ray.h"
```

#### sphere.h

```cpp
#include "hittable.h"
// #include "vec3.h"
```

#### color.h

```cpp
//#include "vec3.h"
```

#### vec3.h

```cpp
//#include <cmath>
//#include <iostream>
```