The **`cproj`** function computes the projection of a complex number on the #key# Reimann sphere: can be visualized as the complex number plane wrapped around a sphere  #key#. 

# Syntax
```c
double complex cproj(double complex z);
```

# Library
The `cproj` function is accessible via the `math.h` library. To access complex numbers, we must include the `complex.h`. 

# Parameter
The `cproj` function takes a single parameter: a complex number, the projection of which is also required. 

# Return value
The function returns the projection of the argument on the Reimann sphere as a complex number. 

>The `cproj` function maps all infinities (e.g. $\infty$+3i, $\infty$-7) to one infinity (i.e., $\infty$).

# Code
The `cproj` function returns a complex number, while `creal` function returns the real part of the complex number and `cimag` returns the imaginary of the complex number.

The following code shows some examples of the use of `cproj` function.

#include <stdio.h>
#include <math.h>
#include <complex.h>
 
int main()
{
    double complex num1 = cproj(3 + 4*I);
    printf("cproj(3 + 4i) = %.1f% + .1fi\n", creal(num1), cimag(num1));
    // %.1f specifies precision of the given float number to 1 decimal place

    double complex num2 = cproj(INFINITY + 2.0*I);
    printf("cproj(inf + 2i) = %.1f% + .1fi\n", creal(num2), cimag(num2));
 
}

What is cproj in C?

The cproj function projects a complex number onto the Riemann sphere, mapping all infinities to a single infinity. It is included in the math.h and complex.h libraries.