Header File 

math.h  

Category 

Math Routines 

Prototype 

double tan(double x); 

long double tanl(long double x); 

Description 

Calculates the tangent. 

tan calculates the tangent. Angles are specified in radians. 

tanl is the long double version; it takes a long double argument and returns a long double result. Error handling for these routines can be modified through the functions _matherr and _matherrl.. 

Return Value 

tan and tanl return the tangent of x, sin(x)/cos(x). 

Example  

#include <stdio.h>
#include <math.h>
int main(void)
{
   double result, x;
   x = 0.5;
   result = tan(x);
   printf("The tan of %lf is %lf\n", x, result);
   return 0;
}

Portability