acospi

Compute the arccosine of the input real number and divide the arccosine by π.

Interface Definition

C interface:

float acospif(float x);

double acospi(double x);

Parameters

Parameter	Type	Description	Input/Output
x	For acospif, x is of single-precision floating-point type. For acospi, x is of double-precision floating-point type.	Floating-point value of a cosine value.	Input

Return Value

The result y is returned following the formula y = acos(x)/π. y ∈ [0, 1]
If the input is ±0, the return value is 0.5.
If the input x is 1, the return value is +0.
If the input x is -1, the return value is 1.
If the input |x| is greater than 1, the return value is NaN.
If the input is ±∞, the return value is NaN.
If the input is ±NaN, the return value is ±NaN.

Dependency

C: "km.h"

Example

C interface:

    // print result
    printf("acospi(0.0) = %.15f\n", acospi(0.0));
    printf("acospi(-0.0) = %.15f\n", acospi(-0.0));
    printf("acospi(0.25) = %.15f\n", acospi(0.25));
    printf("acospi(-0.25) = %.15f\n", acospi(-0.25));
    printf("acospi(0.5) = %.15f\n", acospi(0.5));
    printf("acospi(-0.5) = %.15f\n", acospi(-0.5));
    printf("acospi(1.0) = %.15f\n", acospi(1.0));
    printf("acospi(-1.0) = %.15f\n", acospi(-1.0));
    printf("acospi(INFINITY) = %.15f\n", acospi(INFINITY));
    printf("acospi(-INFINITY) = %.15f\n", acospi(-INFINITY));
    printf("acospi(NAN) = %.15f\n", acospi(NAN));
    printf("acospi(-NAN) = %.15f\n", acospi(-NAN));
    /* 
     * acospi(0.0) = 0.500000000000000
     * acospi(-0.0) = 0.500000000000000
     * acospi(0.25) = 0.419569376744834
     * acospi(-0.25) = 0.580430623255166
     * acospi(0.5) = 0.333333333333333
     * acospi(-0.5) = 0.666666666666667
     * acospi(1.0) = 0.000000000000000
     * acospi(-1.0) = 1.000000000000000
     * acospi(INFINITY) = nan
     * acospi(-INFINITY) = nan
     * acospi(NAN) = nan
     * acospi(-NAN) = -nan
     * 
     * */

Parent topic: Trigonometric Functions