$\frac{1}{sec\theta\:\:tan\theta\:}\:=\:csc\theta\:-sin\theta\:$

$\lim_{t\to-1}\left(\frac{t^2+1}{\left(t^3+2\right)\left(t^4+1\right)}\right)$

$5\tan x-6=2$

$\lim_{x\to\infty}\left(x\cdot sinx\right)$

$\lim_{x\to-1}\left(\frac{2x^4+9x^3+9x+16}{x+1}\right)$

$\frac{2t^3-6t^2-20t}{12^3+18t^2-12t}$

$x^2+54x+72$