cos-1(0.73218673816)
There are two interpretations
1.\((a^{-1}=\frac{1}{a})\)
\(cos^{-1}(0.73218673816rad)=\frac{1}{cos(0.73218673816rad)}=1.34460226097\)
\(cos^{-1}(0.73218673816deg)=\frac{1}{cos(0.73218673816deg)}=1.00008165786\)
2. \( (Keys \ of \ the \ pocket \ calculator)\)
\(cos^{-1}(0.73218673816)=acos(0.73218673816)\)
\(=42.93deg =0.749269312889rad\)
Merry Christmas and a happy new year, asinus :- ) !