Question 826591
{{{csc^(-1)(-1)}}} is a reference to an angle. Specifically, it is a reference to the only angle between -90 and 90 (or between {{{-pi/2}}} and {{{pi/2}}}) inclusive whose csc ratio is -1. Hint: Since csc and sin are reciprocals of each other and since the reciprocal of -1 is also -1, this same angle has a sin of -1.<br>
{{{arccos(0)}}} is also a reference to an angle. (It is another way to write {{{cos^(-1)(0)}}}.) Specifically, it is a reference to the only angle between 0 and 180 (or between 0 and {{{pi}}}) inclusive whose cos ratio is 0.<br>
If you haven't already figured out the answer, then it is time to look up your special angles (and start memorizing them).