$\cos\left(\arccos\left(-.1\right)\right)$

$\frac{x}{5}-5\ge2$

$\frac{dy}{dx}=\frac{3y}{3x+y}$

$\lim_{x\to\infty}\left(\frac{sin\left(4x\right)}{tan\left(9x\right)}\right)$

$\frac{12x+10y}{2}=30$

$x\frac{dy}{dx}+y=\frac{y\left(ln\left(y\right)+1\right)}{ln\left(y\right)}$

$\lim_{x\to\infty}\left(\frac{sen\:}{x^3+2x^2-x+1}\right)$