$\lim_{x\to0}\left(\frac{2\cos x-2}{x^2}\right)$

$\int\left(\frac{cot\left(x\right)sen\left(2x\right)}{sen^2\left(x\right)}\right)dx$

$\frac{125-343x^{15}}{5-7}$

$\frac{1-\sin\left(a\right)^2}{\cos\left(a\right)^2}=\frac{1-\sin\left(a\right)}{1+\sin\left(a\right)}$

$\lim_{x\to\frac{1}{2}}\left(\frac{1-2x}{\sqrt{\frac{5}{2}-x^2}-\frac{3}{2}}\right)$

$a^2+4a+3$

$\sqrt{112}$