tan

Interface Definition

C interface:

float tanf(float x);

double tan(double x);

float complex ctanf(float complex x);

double complex ctan(double complex x);

Fortran interface:

RES = TANF(X);

RES = TAN(X);

RES = CTANF(X);

RES = CTAN(X);

Parameters

Return Value

• The tangent y of the radiant angle x is returned. y ∈ (-INF, +INF).
• If the input is +0, the return value is +0.
• If the input is -0, the return value is -0.
• If the input is ±∞, the return value is NaN.
• If the input is NaN, the return value is NaN.

This function has a mathematical pole at π(1/2 + n). Because no general floating-point numbers can accurately represent the value at the pole, the return value for the pole cannot be considered reliable.

Dependencies

C: "km.h"

Fortran: "km.f03"

Examples

C interface:

    double pi = acos(-1); 
    // typical usage 
    double a = pi/3, c = -3*pi/4, d = 0.0; 
    // special handling 
    double b = pi/2, e = INFINITY, f = -INFINITY, g = NAN; 
    double complex k = 0 + 0 * I;
    // print result 
    printf("tan(pi/3) = %.15f\n", tan(a)); 
    printf("tan(-3*pi/4) = %.15f\n", tan(c)); 
    printf("tan(0.0) = %.15f\n", tan(d)); 
    // mathematical poles 
    printf("tan(pi/2) = %.15f\n", tan(b)); 
    printf("tan(INFINITY) = %.15f\n", tan(e)); 
    printf("tan(-INFINITY) = %.15f\n", tan(f)); 
    printf("tan(NAN) = %.15f\n", tan(g)); 
    printf("ctan(0+0*I) = %.15f + %.15f * I\n", creal(ctan(k)), cimag(ctan(k)));
    /* 
     *  tan(pi/3) = 1.732050807568877 
     *  tan(-3*pi/4) = 1.000000000000000 
     *  tan(0.0) = 0.000000000000000 
     *  tan(pi/2) = 16331239353195370.000000000000000 
     *  tan(INFINITY) = nan 
     *  tan(-INFINITY) = nan 
     *  tan(NAN) = nan 
     *  ctan(0+0*I) = 0 + 0 * I
     * 
     * */

Fortran interface:

    REAL(8) :: X = 0.0 
    PRINT*,  TAN(X) 
    ! 
    ! OUTPUT 
    !     0.000000000000000 
    !