$\lim_{x\to0}\left(\frac{1-\cos\left(x\right)}{2}\right)$

$1+\tan^2\left(a\right)=\sec^2\left(a\right)$

$3y\left(7xy^3-6x^2-4yz\right)$

$\frac{d}{dx}\left(y\left(x^2+49\right)=98\right)$

$x^2-6x+1+x^2+3x$

$\left(x-y+z\right)\left(x+y-z\right)$

$\frac{2\:tan\:x}{1\:+tan\:x}=sen^2x$