# tan Function

Calculates the trigonometric tangent function of a double precision floating-point value.

Include

<math.h>

Prototype

double tan(double x);

Argument

 x value for which to return the tangent

Return Value

Returns the tangent of x specified in radians in the range [-1, 1] . NaN is returned if x is ±∞ .

Example

See the notes at the beginning of this chapter or section for information on using printf() or scanf() (and other functions reading and writing the stdin or stdout streams) in the example code.

#include <math.h>
#include <stdio.h>
#include <errno.h>

int main(void)
{
double x, y;

errno = 0;
x = -1.0;
y = tan (x);
if (errno)
perror("Error");
printf("The tangent of %f is %f\n", x, y);

errno = 0;
x = 0.0;
y = tan (x);
if (errno)
perror("Error");
printf("The tangent of %f is %f\n", x, y);
}

Example Output

The tangent of -1.000000 is -1.557408
The tangent of 0.000000 is 0.000000