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/*
cacos.c
Contributed by Danny Smith
2003-10-20
*/
#include <math.h>
#include <complex.h>
#if 0
/* cacos (Z) = -I * clog(Z + I * csqrt(1 - Z * Z)) */
double complex cacos (double complex Z)
{
double complex Res;
double x, y;
x = __real__ Z;
y = __imag__ Z;
if (y == 0.0)
{
__real__ Res = acos (x);
__imag__ Res = 0.0;
}
else
{
double complex ZZ;
/* Z * Z = ((x - y) * (x + y)) + (2.0 * x * y) * I */
/* caculate 1 - Z * Z */
__real__ ZZ = 1.0 - (x - y) * (x + y);
__imag__ ZZ = -2.0 * x * y;
Res = csqrt(ZZ);
/* calculate ZZ + I * sqrt (ZZ) */
__real__ ZZ = x - __imag__ Res;
__imag__ ZZ = y + __real__ Res;
ZZ = clog(ZZ);
/* mult by -I */
__real__ Res = __imag__ ZZ;
__imag__ Res = - __real__ ZZ;
}
return Res;
}
#else
/* cacos ( Z ) = pi/2 - casin ( Z ) */
double complex cacos (double complex Z)
{
double complex Res = casin (Z);
__real__ Res = M_PI_2 - __real__ Res;
__imag__ Res = - __imag__ Res;
return Res;
}
#endif
#if 0
#include <stdio.h>
int main()
{
double z;
double complex bar = 0.7 + 1.2 * I;
double complex foo = cacos (bar);
printf ("%.16e\t%.16e\n", __real__ foo, __imag__ foo);
foo = cacos (bar);
printf ("%.16e\t%.16e\n", __real__ foo, __imag__ foo);
return 1;
}
#endif
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