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/*
casin.c
Contributed by Danny Smith
2003-10-20
*/
#include <math.h>
#include <complex.h>
/* casin (Z ) = -I * clog(I * Z + csqrt (1.0 - Z * Z))) */
double complex casin (double complex Z)
{
double complex Res;
double x, y;
x = __real__ Z;
y = __imag__ Z;
if (y == 0.0)
{
__real__ Res = asin (x);
__imag__ Res = 0.0;
}
else /* -I * clog(I * Z + csqrt(1.0 - Z * Z))) */
{
double complex ZZ;
/* Z * Z = ((x - y) * (x + y)) + (2.0 * x * y) * I */
/* calculate 1 - Z * Z */
__real__ ZZ = 1.0 - (x - y) * (x + y);
__imag__ ZZ = -2.0 * x * y;
ZZ = csqrt (ZZ);
/* add I * Z to ZZ */
__real__ ZZ -= y;
__imag__ ZZ += x;
ZZ = clog (ZZ);
/* mult by -I */
__real__ Res = __imag__ ZZ;
__imag__ Res = - __real__ ZZ;
}
return (Res);
}
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