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atan, atanf, atanl

From cppreference.com
< c‎ | numeric‎ | math
 
 
 
Common mathematical functions
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Macro constants
 
Defined in header <math.h>
float       atanf( float arg );
(1) (since C99)
double      atan( double arg );
(2)
long double atanl( long double arg );
(3) (since C99)
Defined in header <tgmath.h>
#define atan( arg )
(4) (since C99)
1-3) Computes the principal value of the arc tangent of arg
4) Type-generic macro: If the argument has type long double, atanl is called. Otherwise, if the argument has integer type or the type double, atan is called. Otherwise, atanf is called. If the argument is complex, then the macro invokes the corresponding complex function (catanf, catan, catanl)

Contents

[edit] Parameters

arg - floating point value

[edit] Return value

If no errors occur, the arc tangent of arg (arctan(arg)) in the range [-
π
2
 ; +
π
2
]
radians, is returned.

If a range error occurs due to underflow, the correct result (after rounding) is returned.

[edit] Error handling

Errors are reported as specified in math_errhandling

If the implementation supports IEEE floating-point arithmetic (IEC 60559),

  • If the argument is ±0, it is returned unmodified
  • If the argument is +∞, +π/2 is returned
  • If the argument is -∞, -π/2 is returned
  • if the argument is NaN, NaN is returned

[edit] Notes

POSIX specifies that in case of underflow, arg is returned unmodified, and if that is not supported, and implementation-defined value no greater than DBL_MIN, FLT_MIN, and LDBL_MIN is returned.

[edit] Example

#include <stdio.h>
#include <math.h>
 
int main(void)
{
    printf("atan(1) = %f, 4*atan(1)=%f\n", atan(1), 4*atan(1));
    // special values
    printf("atan(Inf) = %f, 2*atan(Inf) = %f\n", atan(INFINITY), 2*atan(INFINITY));
    printf("atan(-0.0) = %+f, atan(+0.0 = %+f\n", atan(-0.0), atan(0));
}

Output:

atan(1) = 0.785398, 4*atan(1)=3.141593
atan(Inf) = 1.570796, 2*atan(Inf) = 3.141593
atan(-0.0) = -0.000000, atan(+0.0 = +0.000000

[edit] See also

computes arc tangent, using signs to determine quadrants
(function) [edit]
(C99)(C99)
computes arc sine (arcsin(x))
(function) [edit]
(C99)(C99)
computes arc cosine (arccos(x))
(function) [edit]
(C99)(C99)
computes tangent (tan(x))
(function) [edit]
(C99)(C99)(C99)
computes the complex arc tangent
(function) [edit]