\[1)\ y = x^{2} + \cos x\]
\[x \in R;\]
\[y( - x) = ( - x)^{2} + \cos( - x) =\]
\[= x^{2} + \cos x = y(x).\]
\[Ответ:\ \ четная.\]
\[2)\ y = x^{3} - \sin x\]
\[x \in R;\]
\[y( - x) = ( - x)^{3} - \sin( - x) =\]
\[= - x^{3} + \sin x = - y(x).\]
\[Ответ:\ \ нечетная.\]
\[3)\ y = \left( 1 - x^{2} \right)\cos x\]
\[x \in R;\]
\[y( - x) = \left( 1 - ( - x)^{2} \right)\cos( - x) =\]
\[= \left( 1 - x^{2} \right)\cos x = y(x).\]
\[Ответ:\ \ четная.\]
\[4)\ y = \left( 1 + \sin x \right)\sin x\]
\[x \in R;\]
\[y( - x) = \left( 1 + \sin( - x) \right)\sin( - x) =\]
\[= - \left( 1 - \sin x \right)\sin x.\]
\[Ответ:\ \ ни\ четная,\ ни\ нечетная.\]