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<cmath>
double atan ( double x );
float atan ( float x );
long double atan ( long double x );
Compute arc tangent
Returns the principal value of the arc tangent of x, expressed in radians.
In trigonometrics, arc tangent is the inverse operation of tangent.
Notice that because of the sign ambiguity, a function cannot determine with certainty in which quadrant the angle falls only by its tangent value. You can use atan2 if you need to determine the quadrant.
In C++, this function is overloaded in <valarray> (see valarray atan).
Parameters
- x
- Floating point value.
Return Value
Principal arc tangent of x, in the interval [-pi/2,+pi/2] radians.
Portability
In C, only the double version of this function exists with this name.
Example
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/* atan example */
#include <stdio.h>
#include <math.h>
#define PI 3.14159265
int main ()
{
double param, result;
param = 1.0;
result = atan (param) * 180 / PI;
printf ("The arc tangent of %lf is %lf degrees\n", param, result );
return 0;
}
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Output:
The arc tangent of 1.000000 is 45.000000 degrees.
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See also
| atan2 | Compute arc tangent with two parameters (function) |
| tan | Compute tangent (function) |
| sin | Compute sine (function) |
| cos | Compute cosine (function) |
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