What is cos-1(0.8333333)

$$\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{cos}}^{\!\!\mathtt{-1}}{\left({\mathtt{0.833\: \!333\: \!33}}\right)} = {\mathtt{33.557\: \!310\: \!107\: \!427^{\circ}}}$$

I just typed acos(0.833333333) into the calc

$${cos}\left({\mathtt{\,-\,}}{\mathtt{1}}{\mathtt{\,\times\,}}\left({\mathtt{0.833\: \!333\: \!3}}\right) = {\mathtt{\,-\,}}{\mathtt{0.833\: \!333\: \!3}}{\mathtt{\,\small\textbf+\,}}ABC$$

 cos-1(0.8333333)  =  cos-1(5 / 6 )  =  about 33.56°

[ This angle could also lie in the 4th quadrant  ....  ]