C atan() function

C atan() function - Calculate Arctangent


double atan(double x)

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


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);


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

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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