\[\boxed{\mathbf{86.}}\]
\[\textbf{а)}\ y = \sqrt[3]{x} \cdot \sqrt[4]{2 - x}\]
\[\textbf{б)}\ y = 2^{x} \cdot \sin x\]
\[\textbf{в)}\ y = tgx \cdot \log_{3}x\]
\[\textbf{г)}\ y = ctgx \cdot \sqrt[3]{x^{2}}\]