Question

Cot y, if csc y =-10/3 and cos y< 0

Answer 1

$\csc y=-\dfrac{10}3\implies\sin y=-\dfrac3{10}$

$\cos^2y=1-\sin^2y\implies \cos y=\pm\sqrt{1-\dfrac9{100}}=\pm\dfrac{\sqrt{91}}{10}$

You're told that $\cos y$, so omit the positive root.

$\cot y=\dfrac{\cos y}{\sin y}=\dfrac{-\frac{\sqrt{91}}{10}}{-\frac3{10}}=\dfrac{\sqrt{91}}3$