atan, atanf, atanl- Arc tangent

Definition	#include <math.h> double atan(double x); float atanf(float x); (C11) long double atanl(long double x); (C11) These functions are the inverse function of the corresponding tan-functions. They return the principal value (i.e. corresponding angle in radians) of the arc tangent of a floating-point number x.
Return val.	arc tangent(x)  a floating-point number of type double from the interval [-pi/2, +pi/2].
Example	The following program calculates and prints the arc tangent of an input value: #include <math.h> #include <stdio.h> int main(void) { double x; printf("For which number do you want ATAN computed?: \n"); if( scanf("%lf", &x) == 1) /* Verifies the input of a number */ printf("x = %g : atan(%g) = %g\n", x, x, atan(x)); return 0; }
See also	atan2, tan, sin, asin, cos, acos