Macros
#define	PRECISION 9

#define	M_PI 3.141592653589793238462643

Functions
double	cos (double x)

Variables
static double	cos_off_tbl [] = {0.0, -M_PI/2., 0, -M_PI/2.}

static double	cos_sign_tbl [] = {1,-1,-1,1}

Macro Definition Documentation

◆ M_PI

#define M_PI 3.141592653589793238462643

Definition at line 15 of file cos.c.

◆ PRECISION

#define PRECISION 9

Definition at line 14 of file cos.c.

Function Documentation

◆ cos()

double cos ( double x )

Definition at line 21 of file cos.c.

{
    int quadrant;
    double x2, result;
 
    /* Calculate the quadrant */
    quadrant = (int)(x * (2./M_PI));
 
    /* Get offset inside quadrant */
    x = x - quadrant * (M_PI/2.);
 
    /* Normalize quadrant to [0..3] */
    quadrant = quadrant & 0x3;
 
    /* Fixup value for the generic function */
    x += cos_off_tbl[quadrant];
 
    /* Calculate the negative of the square of x */
    x2 = - (x * x);
 
    /* This is an unrolled taylor series using <PRECISION> iterations
     * Example with 4 iterations:
     * result = 1 - x^2/2! + x^4/4! - x^6/6! + x^8/8!
     * To save multiplications and to keep the precision high, it's performed
     * like this:
     * result = 1 - x^2 * (1/2! - x^2 * (1/4! - x^2 * (1/6! - x^2 * (1/8!))))
     */
 
    /* Start with 0, compiler will optimize this away */
    result = 0;
 
#if (PRECISION >= 10)
    result += 1./(1.*2*3*4*5*6*7*8*9*10*11*12*13*14*15*16*17*18*19*20);
    result *= x2;
#endif
#if (PRECISION >= 9)
    result += 1./(1.*2*3*4*5*6*7*8*9*10*11*12*13*14*15*16*17*18);
    result *= x2;
#endif
#if (PRECISION >= 8)
    result += 1./(1.*2*3*4*5*6*7*8*9*10*11*12*13*14*15*16);
    result *= x2;
#endif
#if (PRECISION >= 7)
    result += 1./(1.*2*3*4*5*6*7*8*9*10*11*12*13*14);
    result *= x2;
#endif
#if (PRECISION >= 6)
    result += 1./(1.*2*3*4*5*6*7*8*9*10*11*12);
    result *= x2;
#endif
#if (PRECISION >= 5)
    result += 1./(1.*2*3*4*5*6*7*8*9*10);
    result *= x2;
#endif
    result += 1./(1.*2*3*4*5*6*7*8);
    result *= x2;
 
    result += 1./(1.*2*3*4*5*6);
    result *= x2;
 
    result += 1./(1.*2*3*4);
    result *= x2;
 
    result += 1./(1.*2);
    result *= x2;
 
    result += 1;
 
    /* Apply correct sign */
    result *= cos_sign_tbl[quadrant];
 
    return result;
}

Referenced by __cos(), __libm_sse2_cos(), __libm_sse2_cosf(), __sincos(), _CIcos(), _libm_sse2_cos_precise(), add_arc_part(), AngleBetweenVectorsRad(), attempt_line_merge(), compute_sincos_table(), cosf(), cosl(), create_outline(), D3DRMQuaternionFromRotation(), D3DRMVectorRotate(), draw_cap(), draw_graphics(), DrawGLScene(), EMFDRV_ArcChordPie(), expT(), GdipRotateMatrix(), generateTestSignal(), gl_Lightfv(), gl_rotation_matrix(), Global_Cos(), init_layer3(), IntGdiAngleArc(), IntGdiWidenPath(), Math_cos(), CDrvDefExt::PaintStaticControls(), PATH_DoArcPart(), polar(), powT(), prepare_decode_tables(), pres_cos(), render(), RotatePoint(), rpn_cos(), shorten_line_percent(), sincos(), Test_cos_approx(), Test_cos_exact(), ValarrayTest::transcendentals(), and unstretch_angle().

Variable Documentation

◆ cos_off_tbl

double cos_off_tbl[] = {0.0, -M_PI/2., 0, -M_PI/2.}

static

Definition at line 17 of file cos.c.

Referenced by cos().

◆ cos_sign_tbl

double cos_sign_tbl[] = {1,-1,-1,1}