double cos
(
double x /* angle in radians */
)
{
double a,c,z,s = 1.0;
if(!finite(x)) /* cos(NaN) and cos(INF) must be NaN */
return x-x;
x=drem(x,PI2); /* reduce x into [-PI,PI] */
a=copysign(x,one);
if (a >= PIo4) {
if (a >= PI3o4) { /* ... in [3PI/4,PI] */
a = PI-a;
s = negone;
}
else { /* ... in [PI/4,3PI/4] */
a = PIo2-a;
return a+a*sin__S(a*a); /* rtn. S(PI/2-|x|) */
}
}
if (a < small) {
big+a;
return s; /* rtn. s*C(a) */
}
z = a*a;
c = cos__C(z);
z *= half;
a = (z >= thresh ? half-((z-half)-c) : one-(z-c));
return copysign(a,s);
}
double sin
(
double x /* angle in radians */
)
{
double a,c,z;
if(!finite(x)) /* sin(NaN) and sin(INF) must be NaN */
return x-x;
x=drem(x,PI2); /* reduce x into [-PI,PI] */
a=copysign(x,one);
if (a >= PIo4) {
if(a >= PI3o4) /* ... in [3PI/4,PI] */
x = copysign((a = PI-a),x);
else { /* ... in [PI/4,3PI/4] */
a = PIo2-a; /* rtn. sign(x)*C(PI/2-|x|) */
z = a*a;
c = cos__C(z);
z *= half;
a = (z >= thresh ? half-((z-half)-c) : one-(z-c));
return copysign(a,x);
}
}
if (a < small) { /* rtn. S(x) */
big+a;
return x;
}
return x+x*sin__S(x*x);
}
double
tan(double x)
{
double a;
double z;
double ss;
double cc;
double c;
int k;
if(!finite(x)) /* tan(NaN) and tan(INF) must be NaN */
return x-x;
x = drem(x,PI); /* reduce x into [-PI/2, PI/2] */
a = copysign(x,one); /* ... = abs(x) */
if (a >= PIo4) {
k = 1;
x = copysign(PIo2-a,x);
}
else {
k = 0;
if (a < small) {
(void volatile)(big+a);
return x;
}
}
z = x*x;
cc = cos__C(z);
ss = sin__S(z);
z *= half; /* Next get c = cos(x) accurately */
c = (z >= thresh ? half-((z-half)-cc) : one-(z-cc));
if (k == 0) {
return x+(x*(z-(cc-ss)))/c; /* ... sin/cos */
#ifdef national
} else if (x == zero) {
return copysign(fmax,x); /* no inf on 32k */
#endif /* national */
} else {
return c/(x+x*ss); /* ... cos/sin */
}
}
