# C atan() function

## C atan() function - Calculate Arctangent

Syntax:

`double atan(double x)`

The atan() function is used to calculate the arctangent of x.

Parameters:

Name Description Required /Optional
x This is the floating point value. Required

Return value from atan()

• The atan() function returns a value in the range -π/2 to π/2 radians.

Example: atan() function

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

``````
#include <stdio.h>
#include <math.h>
int main(void)
{
double a,c;
c = 0.45;
a = atan(c);

printf("atan( %lf ) = %lf", c, a);
c = 0;
a = atan(c);

printf("\natan( %lf ) = %lf", c, a);

c = 1;
a = atan(c);

printf("\natan( %lf ) = %lf", c, a);
}
``````

Output:

```atan( 0.450000 ) = 0.422854
atan( 0.000000 ) = 0.000000
atan( 1.000000 ) = 0.785398
```

C Programming Code Editor:

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## 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