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

$\frac{cos^3\left(a\right)-cos\left(a\right)+sen\left(a\right)}{cos\left(a\right)}=\tan\left(a\right)-\:sin^2\left(a\right)$

$36x^2-y^4$

$\int ye^{6y^2}dy$

$\int x\left(4x^2-3\right)dx$

$\int\frac{x^5}{\sqrt{9-x^2}}dx$

$\cot\left(x\right)=-5$