// csinh(conj(z)) = conj(csinh(z)) and csinh is odd.
// csinh(+0 + i0) returns +0 + i0.
// csinh(+0 + i<><69>) returns <20>}0 + iNaN (where the sign of the real part of the result is unspecified) and raises the <20>e<EFBFBD>einvalid<69>f<EFBFBD>f floating-point exception.
// csinh(+0 + iNaN) returns <20>}0 + iNaN (where the sign of the real part of the result is unspecified).
// csinh(x + i<><69>) returns NaN + iNaN and raises the <20>e<EFBFBD>einvalid<69>f<EFBFBD>f floating-point exception, for positive finite x.
// csinh(x + iNaN) returns NaN + iNaN and optionally raises the <20>e<EFBFBD>einvalid<69>f<EFBFBD>f floating-point exception, for finite nonzero x.
// csinh(+<2B><>+ i0) returns +<2B><>+ i0.
// csinh(+<2B><>+ iy) returns +<2B><> cis(y), for positive finite y.
// csinh(+<2B><>+ i<><69>) returns <20>}<7D><>+ iNaN (where the sign of the real part of the result is unspecified) and raises the <20>e<EFBFBD>einvalid<69>f<EFBFBD>f floating-point exception.
// csinh(+<2B><>+ iNaN) returns <20>}<7D><>+ iNaN (where the sign of the real part of the result is unspecified).
// csinh(NaN + i0) returns NaN + i0.
// csinh(NaN + iy) returns NaN + iNaN and optionally raises the <20>e<EFBFBD>einvalid<69>f<EFBFBD>f floating-point exception, for all nonzero numbers y.