$\left(2\right)\frac{1}{2}x^2$

$\frac{\cos^2\left(x\right)-\sin^2\left(x\right)}{\sin\left(x\right)}$

$18\cdot4+18-\left(-2\right)-11$

$\left(x-2\right)\left(x^2-1\right)-\left(x^2-2\right)\left(3-x\right)$

$s^3\:x\:s^{-7}$

$9y-z-2y+5x-8z-7y$

$\log_{10}\left(8\right)+\left(x^2-5x+7\right)\cdot\log_{10}\left(3\right)=\log_{10}\left(24\right)$