$2\cos^2x\cdot\sin x+\cos x=0$

$15-27:\left(1+2\cdot4\right)-3\cdot\left(-1\right)$

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

$-\frac{\cos\left(x\right)}{1-\sin\left(x\right)}+\frac{\cos\left(x\right)}{1+\sin\left(x\right)}=2\tan\left(x\right)$

$\left(2i\right)\left(1-i\right)$

$v^2+10v+25$

$a\cdot\left(m^2-n^2+amn\right)$