函數(shù)展開(kāi)成x+4的冪級(jí)數(shù)為()
A.A B.B C.C D.D
函數(shù)f(x)=cos2x(-∞<x<+∞)展開(kāi)成x的冪級(jí)數(shù)為()
冪級(jí)數(shù)的和函數(shù)是()