$2\cos^2\left(x\right)-\cos\left(x-1\right)$

$\frac{\cot\left(x\right)-\tan\left(x\right)}{\cos\left(x\right)+\sin\left(x\right)}$

$x2y\:+\:xy2$

$\log\frac{1}{2}x$

$-x^4-x^2;\:x=10$

$\frac{d^{12}}{dx^{12}}\left(x^3+1\right)$

$\lim_{x\to3}\left(\frac{\sqrt{x+1}-2}{\sqrt{2x+3}}\right)$