$\cot\left(a\right)-\tan\left(a\right)=2\cot\left(2a\right)$

$cos3x-cosx$

$\lim_{x\to3}\left(-\sqrt{x+5}\right)$

$6x^2+19x-10=0$

$\int x^3\:\sqrt{a^2-2}dx$

$\int_0^{\infty}\left(\frac{sin\left(\sqrt{x}\right)+4}{x^2}\right)dx$

$\int\frac{x+3}{x\left(1+x^2\right)}dx$