G.6.1.1 The cacos functions

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• cacos(conj(z)) = conj(cacos(z)).

• cacos((+-)0 + i0) returns pi /2 - i0.

• cacos((+-)0 + iNaN) returns pi /2 + iNaN.

• cacos(x + i (inf)) returns pi /2 - i (inf), for finite x.

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

• cacos(-(inf) + iy) returns pi - i (inf), for positive-signed finite y.

• cacos(+(inf) + iy) returns +0 - i (inf), for positive-signed finite y.

• cacos(-(inf) + i (inf)) returns 3pi /4 - i (inf).

• cacos(+(inf) + i (inf)) returns pi /4 - i (inf).

• cacos((+-)(inf) + iNaN) returns NaN (+-) i (inf) (where the sign of the imaginary part of the result is unspecified).

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

• cacos(NaN + i (inf)) returns NaN - i (inf).

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