$19.3\left(1.089\right)^{23.1}$

$\lim_{x\to0}\left(\frac{ln\left(sec\left(x\right)\right)}{x}\right)$

$\frac{dy}{dx}=14\left(1+y^2\right)x^2$

$-ydx+\left(x+y\right)dy=0$

$\lim_{x\to3}\left(\frac{x^2-9}{x^3+3x^2-4x+12}\right)$

$\frac{8a^6a^4}{4a^{-3}}$

$\frac{dy}{dx}\left(2\sqrt{x-1}\arccsc\left(\sqrt{x}\right)\right)$