tan

接口定义

C interface:

float tanf(float x);

double tan(double x);

Fortran interface:

RES = TANF(X);

RES = TAN(X);

参数

返回值

1. 返回弧度角x的正切函数值y，y ∈ (-INF, +INF)。
2. 输入+0，返回+0。
3. 输入-0，返回-0。
4. 输入±∞，返回nan。
5. 输入nan，返回nan。

• 该函数在 π(1/2 + n) 处具有数学极点；没有通用的浮点表示能够精确地表示极点处的值，因此极点处会返回值，但不能认为是正确的。

依赖

C: "km.h"

Fortran: "km.f03"

示例

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; 
    // 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)); 
    /* 
     *  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 
     * 
     * */

Fortran interface:

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