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

$\int4x^3e^{2x}dx$

$ln\left(\frac{3-x-x^2}{\sqrt{2+x-x^2}}\right)$

$0,1\cdot\frac{di}{dt}+50\cdot i=50$

$\lim_{x\to0}\left(\frac{\sin\left(1+x\right)-\sin\left(1\right)}{x}\right)$

$[8-x\frac{2}{8}]$

$\int\:\frac{-3}{\sqrt{4x-x^2+1}}dx$