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1、第十章函数项级数习题10.1函数项级数的一致收敛性1.讨论下列函数序列在指定区间上的一致收敛性。⑴S(x)=−nx,(i)xne∈)1,0(,(ii)x∈,1(+∞);⑵S(x)=x−nx,xne∈,0(+∞);x⑶Sn(x)=sin,(i)x∈(−∞,+∞),(ii)x∈[−A,A](A>0);n⑷Sn(x)=arctannx,(i)x∈)1,0(,(ii)x∈,1(+∞);21⑸Sn(x)=x+,x∈(−∞,+∞);2nn⑹Sn(x)=nx(1-x),x∈[]1,0;xx⑺Sn(x)=ln,(i)x∈)1,0(,(ii)x∈,1(+∞));nnnx⑻Sn(x)=
2、,(i)x∈)1,0(,(ii)x∈,1(+∞);n1+xn⑼Sn(x)=(sinx),x∈[,0π];1⑽S(x)=(sinx)n,(i)x∈[0,]π,(ii)x∈[δ,π−δ](δ>0);nn⎛x⎞www.khdaw.com⑾Sn(x)=⎜1+⎟,(i)x∈,0(+∞),(ii)x∈,0(A](A>0);⎝n⎠⎛1⎞⑿Sn(x)=n⎜x+−x⎟⎟,(i)x∈,0(+∞),(ii)x∈[δ,+∞),δ>0。⎜n⎝⎠解(1)(i)S(x)=0,d(Sn,S)=supSn(x)−S(x)=1─/→0(n→∞),课后答案网x∈)1,0(所以{Sx()}在(0,1)上非
3、一致收敛。n(ii)S(x)=0,−nd(Sn,S)=supSn(x)−S(x)=e→0(n→∞),x∈,1(+∞)所以{Sx()}在(1,+∞)上一致收敛。n(2)S(x)=0,1d(Sn,S)=supSn(x)−S(x)=→0(n→∞),x∈,0(+∞)ne1所以{Sx()}在(0,+∞)上一致收敛。n(3)(i)S(x)=0,d(Sn,S)=supSn(x)−S(x)=1─/→0(n→∞),x∈(−∞,+∞)所以{Sx()}在(,−∞+∞)上非一致收敛。n2A(ii)S(x)=0,当n>,πAd(Sn,S)=supSn(x)−S(x)≤→0(n→∞),x∈[−
4、A,A]n所以{Sx()}在[,−AA]上一致收敛。nπ(4)(i)S(x)=,2πd(Sn,S)=supSn(x)−S(x)=─/→0(n→∞),x∈)1,0(2所以{Sx()}在(0,1)上非一致收敛。nπ(ii)S(x)=,www.khdaw.com2πd(Sn,S)=supSn(x)−S(x)=−arctann→0(n→∞),x∈,1(+∞)2所以{Sx()}在(1,+∞)上一致收敛。n211(5)S(x)=x,由于Sn(x)−S(x)=x+−x≤,于是2n课后答案网nd(Sn,S)=supSn(x)−S(x)→0(n→∞),x∈(−∞,+∞)所以{Sx()
5、}在(,−∞+∞)上一致收敛。n(6)S(x)=0,111nSn()−S()=1(−)─/→0(n→∞),nnn所以{Sx()}在[0,1]上非一致收敛。n(7)(i)S(x)=0,由于Sn0(+)−S0(+)=0,且2d1x[]Sn(x)−S(x)=1(+ln)<0(n≥)2,dxnn于是lnnd(Sn,S)=supSn(x)−S(x)=→0(n→∞),x∈)1,0(n所以{Sx()}在(0,1)上一致收敛。n(ii)S(x)=0,Sn2(n)−S2(n)=2ln2─/→0(n→∞),所以{Sx()}在(1,+∞)上非一致收敛。n(8)(i)S(x)=0,1n1(
6、−)11nSn1(−)−S1(−)=─/→0(n→∞),nn1n1+1(−)n所以{Sx()}在(0,1)上非一致收敛。nwww.khdaw.com(ii)S(x)=1,1n1(+)11nSn1(+)−S1(+)=−1─/→0(n→∞),nn1n1+1(+)n所以{Sx()}在(1,+∞)上非一致收敛。n课后答案网⎧π1x=⎪⎪21π(9)S(x)=⎨,取xn∈,0[π],使得sinxn=1−,则xn≠,⎪πn20x∈,0[π],x≠⎪⎩21nSn(xn)−S(xn)=1(−)─/→0(n→∞),n所以{Sx()}在[0,]π上非一致收敛。n⎧0x=,0π1(10)
7、(i)S(x)=⎨,取xn∈,0(π),使得sinxn=n,则⎩10