C Tutorial/math.h/atan
atan
Item Value Header file math.h Declaration float atanf(float arg);double atan(double arg);long double atanl(long double arg); Return returns the arc tangent of arg.
#include <math.h>
#include <stdio.h>
int main(void)
{
double val = -1.0;
do {
printf("Arc tangent of %f is %f.\n", val, atan(val));
val += 0.1;
} while(val<=1.0);
return 0;
}