$\cos^2u-\sec^2u=1-2\:sen^2$

$x^2+\frac{7}{6}+\frac{49}{24}$

$y^2=x^2\cdot\left(2-x\right)$

$\left(\frac{-7}{11}z^3y^3+\frac{5}{14}y^2z^5\right)^2$

$-21-\left(-112\right)-79$

$-\left\{-3+4-\left(-2-3-5\right)+\left[+\left(-2+4\right)-2\right]\right\}$

$\lim_{x\to\infty}\left(\frac{1}{e^x+1}\right)$