$f\left(x\right)=\sqrt{x^2}-4$

$\frac{d}{dx}\sqrt{\frac{x\left(x+6\right)}{\left(7x+1\right)\left(7x+2\right)}}$

$h\left(x\right)=x^2+6x+9$

$\frac{-4x^5+6x+8}{2x^2}$

$-\frac{1}{2}\le\frac{x}{1+x^2}$

$\sin\left(85\right)=\cos\left(40\right)$