The function double atan(double x); returns the arc tangent of x, expressed in radians. Arc tangent is the inverse operation of tangent.
Function prototype of atan
double atan(double x);
- x : A floating point value whose arc tangent(inverse tangent) to be computed, in the interval [-INFINITY, INFINITY].
Return value of atan
Function atan returns the principal arc tangent of x, in the interval [-Pi/2, +Pi/2] radians.
C program using atan function
The following program shows the use of atan function to calculate inverse of tangent.
#include <stdio.h>
#include <math.h>
#define PI 3.14159
int main(){
double input, radian, degree;
/* Range of tan function is -INFINITY to +INFINITY */
printf("Enter a number between -INFINITY to +INFINITY\n");
scanf("%lf", &input);
radian = atan(input);
/*
* Radian to degree conversion
* One radian is equal to 180/PI degrees.
*/
degree = radian * (180.0/PI);
printf("The arc tan of %0.4lf is %0.4lf in radian\n",
input, radian);
printf("The arc tan of %0.4lf is %0.4lf in degree\n",
input, degree);
return 0;
}
Output
Enter a number between -INFINITY to +INFINITY 1.0 The arc tan of 1.0000 is 0.7854 in radian The arc tan of 1.0000 is 45.0000 in degree
Enter a number between -INFINITY to +INFINITY 9999.0 The arc tan of 9999.0000 is 1.5707 in radian The arc tan of 9999.0000 is 89.9943 in degree