\[1)\ y = \left| \cos x \right|\]
\[2)\ y = 3 - 2\cos(x - 1)\]
\[3)\ y = \sin x \bullet ctg\ x\]
\[y = \sin x \bullet \frac{\cos x}{\sin x} = \cos x\]
\[\sin x \neq 0;\ \ \ x \neq \pi\text{n.}\]
\[4)\ y = 2^{\cos x}\]
\[\cos x = 1:\]
\[y = 2^{1} = 2.\]
\[\cos x = 0:\]
\[y = 2^{0} = 1.\]
\[\cos x = - 1:\]
\[y = 2^{- 1} = 0,5.\]