$\frac{\left(\csc^2\left(x\right)-1\right)}{\csc^2\left(x\right)-\csc\left(x\right)}$

$-3a^3+2b+5a^3$

$x^2-x-600$

$\sin^2\left(x\right)\tan^4\left(x\right)$

$\lim_{x\to\infty}\frac{2x+5}{3x^2+1}$

$\lim_{x\to\frac{\pi}{2}}\left(\frac{tan\left(26x\right)}{tan\left(21x\right)}\right)$

$3\sqrt{3n^3}-9$