数学试题讲解

设

M = \int_{- \frac{π}{2}}^{\frac{π}{2}} \frac{\sin x}{1 + x^{2}} \cos^{4} x d x, N = \int_{\frac{- π}{2}}^{\frac{π}{2}} (\sin^{3} x + \cos^{4} x) d x, P = \int_{- \frac{π}{2}}^{\frac{π}{2}} (x^{2} \sin^{3} x - \cos^{4} x) d x

,则 M、N、P 的大小关系为