$\frac{dy}{dt}=\frac{t+1}{ty+t}$

$\sqrt{4x}\sqrt{20x^3}$

$\sec^2x-1\left(x\right)^2=\frac{1}{\sin\left(x\right)^2\cdot\cos\left(x\right)^2}$

$\lim_{x\to0}\left(\frac{\cos\left(z+a\right)-\cos\left(z-a\right)}{x}\right)$

$\lim_{x\to\infty}\left(\frac{3x+2}{7}\right)$

$\frac{2}{\sqrt{b}+3}$

$\frac{60}{4}$