# C cos() function

## C cos() function - arc cosine functions

**Syntax:**

double cos(double x)

The cos() function is used to calculate the cosine of x. The value x is expressed in radians. If x is too large, a partial loss of significance in the result might occur.

**Parameters:**

Name | Description | Required /Optional |
---|---|---|

x | Represent an angle expressed in radians. | Required |

**Return value from cos()**

- The function returns the cosine of x.

**Example: cos() function**

The following example shows the usage of cos() function.

```
#include <math.h>
#include <stdio.h>
int main(void)
{
double x, y;
x = 0;
y = cos(x);
printf("cos( %lf ) = %lf\n", x, y);
x = 1;
y = cos(x);
printf("\ncos( %lf ) = %lf\n", x, y);
x = 45;
y = cos(x);
printf("\ncos( %lf ) = %lf\n", x, y);
}
```

Output:

cos( 0.000000 ) = 1.000000 cos( 1.000000 ) = 0.540302 cos( 45.000000 ) = 0.525322

**C Programming Code Editor:**

**Previous C Programming:** C atan2()

**Next C Programming: ** C cosh()

## C Programming: Tips of the Day

**What's the point of const pointers?**

const is a tool which you should use in pursuit of a very important C++ concept:

Find bugs at compile-time, rather than run-time, by getting the compiler to enforce what you mean.

Even though it does not change the functionality, adding const generates a compiler error when you're doing things you didn't mean to do. Imagine the following typo:

void foo(int* ptr) { ptr = 0;// oops, I meant *ptr = 0 }

If you use int* const, this would generate a compiler error because you're changing the value to ptr. Adding restrictions via syntax is a good thing in general. Just don't take it too far -- the example you gave is a case where most people don't bother using const.

Ref : https://bit.ly/33Cdn3Q

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