The **`conj()`** function in C reverses the sign of the imaginary part of a complex number to compute its conjugate.

# Library
To use the `conj()` function, include the `complex.h` library as shown below:
```C
#include <complex.h>
```
# Syntax
The `conj()` function is declared as follows:
```C
double complex conj(double complex z);
```
The `conj()` function takes in ﻿﻿the complex number ﻿`z`﻿ as a parameter and returns the conjugate of `z`.

# Code
Consider the code snippet below, which uses `conj()` to compute the conjugate of a complex number:

#include <stdio.h>
#include <complex.h>

int main() {

  double complex complexNumber1 = 1 + I*2;
  double complex complexNumber2 = 1 - I*2;

  double complex conjugate1 = conj(complexNumber1);
  double complex conjugate2 = conj(complexNumber2);

  printf("conj ( %f + %fi ) = ( %f + %fi ) \n", creal(complexNumber1), cimag(complexNumber1) , creal(conjugate1), cimag(conjugate1));
  printf("conj ( %f + %fi ) = ( %f + %fi ) \n", creal(complexNumber2), cimag(complexNumber2) , creal(conjugate2), cimag(conjugate2));
  
  return 0;
}


## Explanation
The `conj()` function is used in lines 9 and 10 to compute the conjugate of the complex numbers `complexNumber1` and `complexNumber2` that are created in lines 6 and 7. 

What is conj() in C?

Conj() in C changes the sign of the imaginary part of a complex number, requiring complex.h.