cos

Compute the cosine of a real number.

Interface Definition

C interface:

float cosf(float x);

double cos(double x);

float complex ccosf(float complex x);

double complex ccos(double complex x);

Fortran interface:

RES = COSF(X);

RES = COS(X);

RES = CCOSF(X);

RES = CCOS(X);

Parameters

Parameter	Type	Description	Input/Output
x	For cosf, x is of single-precision floating-point type. For cos, x is of double-precision floating-point type. For ccosf, x is of single-precision floating-point complex number type. For ccos, x is of double-precision floating-point complex number type.	Floating-point value of a radian angle	Input

Return Value

The cosine y of radiant angle x is returned. y ∈ [-1, +1].
If the input is +0, the return value is +1.
If the input is -0, the return value is +1.
If the input is ±∞, the return value is NaN.
If the input is NaN, the return value is NaN.

Dependencies

C: "km.h"

Fortran: "km.f03"

Examples

C interface:

   double pi = acos(-1); 
    // typical usage 
    double a = pi/3, b = pi/2, c = -3*pi/4, d = 0.0; 
    // special handling 
    double e = INFINITY, f = -INFINITY, g = NAN; 
    double complex k = 0 + 0 * I;
    // print result 
    printf("cos(pi/3) = %.15f\n", cos(a)); 
    printf("cos(pi/2) = %.15f\n", cos(b)); 
    printf("cos(-3*pi/4) = %.15f\n", cos(c)); 
    printf("cos(0.0) = %.15f\n", cos(d)); 
    printf("cos(INFINITY) = %.15f\n", cos(e)); 
    printf("cos(-INFINITY) = %.15f\n", cos(f)); 
    printf("cos(NAN) = %.15f\n", cos(g)); 
    printf("ccos(0+0*I) = %.15f + %.15f * I\n", creal(ccos(k)), cimag(ccos(k)));
    /* 
     *  cos(pi/3) = 0.500000000000000 
     *  cos(pi/2) = 0.000000000000000 
     *  cos(-3*pi/4) = -0.707106781186547 
     *  cos(0.0) = 1.000000000000000 
     *  cos(INFINITY) = nan 
     *  cos(-INFINITY) = nan 
     *  cos(NAN) = nan 
     *  ccos(0+0*I) = 1 + -0 * I
     * 
     * */

Fortran interface:

    REAL(8) :: X = 0.0 
    PRINT*,  COS(X) 
    ! 
    ! OUTPUT 
    !     1.000000000000000 
    !

Parent topic: Function Syntax