$\frac{9y}{3y^{-1}}$

$\lim_{x\to\frac{\pi}{2}}\left(\frac{\sqrt{1-\cos\left(x\right)}-\sqrt{1+\cos\left(x\right)}}{\sqrt{\cot\left(x\right)}}\right)$

$-2x-4b$

$\frac{1}{csc\left(x\right)}-cot\left(x\right)-\frac{1}{\left(sin\left(x\right)\right)}$

$\left(6.6\right)^2$

$16a^4+9b^2+24a^2b$

$-15-\left(-32\right)$