The **`copysign()`** function is used to copy the sign of a number to the magnitude of another number and is a part of the `math.h` header file in C.

# Syntax
The declaration of the `copysign()` function is shown below:
```C
double copysign (double a, double b);
```
The `copysign()` function takes `a` and `b` as parameters and returns a number with the same magnitude as `a` and the same sign as `b`.

# Code
Consider the code snippet below, which shows the implementation of the `copysign()` function:

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

int main() {

  double a = 1.55;
  double b = -2.33;

  double x = copysign(a, b);

  printf("copysign ( %f, %f ) = ( %lf ) \n", a, b, x);
  
  return 0;
}

# Explanation
The `copysign()` function is used in `line 9` to compute a number with the ﻿same magnitude as `a` (create﻿d in `line 6`) and the same sign as `b`(created in `line 7`).

What is copysign() in C?

Syntax

Code

Explanation