$\frac{15x+7\left(x-1\right)}{21}+30=\frac{2\left(x-4\right)+15x}{3}$

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

$x^2+y^2+z^2<4$

$cosx\:secx$

$inversa\:\frac{2x+3}{5-x}$

$\int x^3\left(16+x^2\right)dx$

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