The question reads:
Angles $A$ and $B$ are obtuse angles in quadrant 2 (II). If $\csc A = 3$ and $\tan B$ = -1/3, determine the exact value of $\cos (A+B)$.
How would I take on this question? Generally when I am given $\cos (A+B)$, the two values to insert into the expanded formula are given.
