G.6.2.3 The catanh functions

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• catanh(conj(z)) = conj(catanh(z)) and catanh is odd.

• catanh(+0 + i0) returns +0 + i0.

• catanh(+0 + iNaN) returns +0 + iNaN.

• catanh(+1 + i0) returns +(inf) + i0 and raises the “divide-by-zero” floating-point exception.

• catanh(x + i (inf)) returns +0 + ipi /2, for finite positive-signed x.

• catanh(x + iNaN) returns NaN + iNaN and optionally raises the “invalid” floating-point exception, for nonzero finite x.

• catanh(+(inf) + iy) returns +0 + ipi /2, for finite positive-signed y.

• catanh(+(inf) + i (inf)) returns +0 + ipi /2.

• catanh(+(inf) + iNaN) returns +0 + iNaN.

• catanh(NaN + iy) returns NaN + iNaN and optionally raises the “invalid” floating-point exception, for finite y.

• catanh(NaN + i (inf)) returns (+-)0 + ipi /2 (where the sign of the real part of the result is unspecified).

• catanh(NaN + iNaN) returns NaN + iNaN.