泛函知识点期末总结
一、关于有界线性算子,算子范数等
1、设 x?X?C[a,b],定义X上的线性算子
T:若f?C[a,b],(Tf)(t)?x(t)f(t),t?[a,b]。
求证:T有界,并求||T||。
2、设 X?C[a,b],t0?[a,b]。定义X上的线性泛函f:若x?X,f(x)?x(t0)。求证:f有界,并求||f||。
3、设 X?C[a,b],t1,t2,,tn?[a,b],?1,?2,
n,?3?C(全体复数集),定义X上
的线性泛函f: 若x?X,f(x)???ix(ti),f有界,并求||f||。
i?1
二、关于共轭空间的定义及其求解
三、内积空间的定义及内积空间与赋范空间的关系,常见的内积空间
四、变分引理 极小化向量定理P245定理1及推论,P247引理1,P251引理1
五、投影定理,投影算子及其性质,
六、Hilbert空间的连续线性泛函,共轭算子,自伴算子,正常算子,酉算子
七、完全规范正交基及其判定定理
八、Banach空间的基本定理及其应用
九、Banach共轭算子的定义及其求法
十、逆算子定理与闭图像定理之间的关系与证明
十一、强收敛,弱收敛,弱星收敛,一致收敛及其关系
十二、完备度量空间的定义及其应用
十三、压缩映射原理及其应用
十四、h?lder 不等式,Minkowski不等式,Schwarz不等式
十五、稠密,可分,完备,柯西序列
十六、度量空间定义及其常见度量空间,赋范线性空间的定义及其常见赋范线性
空间
第二篇:实变函数与泛函分析基础第三版(程其襄)+课后答案
1.A∪(B∩C)=(A∪B)∩(A∪C).
x∈(A∪(B∪C)).x∈A,x∈A∪B,x∈A∪C,x∈(A∪B)∩(A∪C).x∈B∩C,x∈A∪Bx∈A∪C,x∈(A∪B)∩(A∪C),
A∪(B∩C)?(A∪B)∩(A∪C).
x∈(A∪B)∩(A∪C).x∈A,x∈A∪(B∩C).x∈A,
x∈A∪Bx∈A∪C,x∈Bx∈C,x∈B∩C,x∈A∪(B∩C),(A∪B)∩(A∪C)?A∪(B∩C).
2.A∪(B∩C)=(A∪B)∩(A∪C).
(1)A?B=A?(A∩B)=(A∪B)?B;
(2)A∩(B?C)=(A∩B)?(A∩C);
(3)(A?B)?C=A?(B∪C);
(4)A?(B?C)=(A?B)∪(A∩C);
(5)(A?B)∩(C?D)=(A∩C)?(B∪D);
(6)A?(A?B)=A∩B.
(1)A?(A∩B)=A∩?s(A∩B)=A∩(?sA∪?sB)=(A∩?sA)∪(A∩?sB)=A?B;(A∪B)?B=(A∪B)∩?sB=(A∩?sB)∪(B∩?sB)=A?B;
(2)(A∩B)?(A∩C)=(A∩B)∩?s(A∩C)=(A∩B)∩(?sA∪?sC)=(A∩B∩?sA)∪(A∩B∩?sC)=A∩(B∩?sC)=A∩(B?C);
(3)(A?B)?C=(A∩?sB)∩?sC=A∩?s(B∪C)=A?(B∪C);
(4)A?(B?C)=A?(B∩?sC)=A∩?s(B∩?sC)=A∩(?sB∪C)=(A∩?sB)∪(A∩C)=(A?B)∪(A∩C);
(5)(A?B)∩(C?D)=(A∩?sB)∩(C∩?sD)=(A∩C)∩?s(B∪D)=(A∩C)?(B∪D);
(6)A?(A?B)=A∩?s(A∩?sB)=A∩(?sA∪B)=A∩B.
3.(A∪B)?C=(A?C)∪(B?C);A?(B∪C)=(A?B)∩(A?C).
(A∪B)?C=(A∪B)∩?sC=(A∩?sC)∪(B∩?sC)=(A?C)∪(B?C);
∞?∞?(A?B)∩(A?C)=(A∩?sB)∩(A∩?sC)=A∩?sB∩?sC=A∩?s(B∪C)=A?(B∪C).
4.?s(
i=1Ai)=
∞?i=1?sAi.
x∈S,x∈∞?x∈?s(
i=1Ai),
i=1Ai,i,x∈Ai,x∈?sAi,
1
x∈
i=1
x∈?s(5.
∞?
?sAi.
i=1
x∈
∞?
i=1
Ai).
∞?
?sAi,
i=1∞?
i,x∈?sAi,
x∈S,x∈Ai,
x∈S,
x∈
?s(Ai)=
i=1
(1)(?
α∈Λ
(1)
(2)6.
α∈Λ
?
α∈Λ
Aα?B=(
α∈Λ
?
Aα)?B=
?
∞?
i=1
?sAi.(Aα?B);
α∈Λ
∞?
Ai,
α∈Λ
Aα)∩?sB=
?
?
(2)(
α∈Λ
Aα?B=(
?
α∈Λ
Aα)∩?sB=
α∈Λ
(Aα∩?sB)=
?
(Aα∩?sB)=
α∈Λ
?
Aα)?B=
?
α∈Λ
{An}
ν=1
i=j,
n?
Aν=
ν=1
n?
B1=A1,Bn=An?(
Bν,1≤n≤∞.i<j.
n?1?ν=1
?
α∈Λ
(Aα?B);
?
(Aα?B).
(Aα?B).
Aν),n>1.
{Bn}
Bi?Ai
(1≤i≤n).
Bi∩Bj?Ai∩(Aj?Bi?Ai(1=i=n)
n=1
j?1?
An)=Ai∩Aj∩?sA1∩?sA2∩···∩?sAi∩···∩?sAj?1=?.
n?
i=1
x∈Ai
x∈
in?1?i=1
i=1
n?
Ai,
x∈A1,
n?
Bi?
i=1
Ai.
n?
x∈B1?
x∈Ain.?
=0,
x∈Ain?
7.
A2n?1
1
i=1in?1?i=1
Bi.
x∈A1,
n?
in
x∈Ain,
Ai=Bin?
i=1
Bi.
i=1
n?
Ai=
i=1
n?
Bi.
n→∞
limAn=(0,∞);
x∈(0,∞),
N,
x<N,x
n>N
0<x<n,
x∈A2n,
x
N
An,
x∈
n→∞
limAn?(0,∞),
n→∞
An=?;x∈lim
n.
n→∞Am.
0<x≤0,
lim
n→∞
An=
n=1m=n
x∈lim
n=1m=n∞?∞?
∞?∞?
n→∞
An?
Am.
x∈
n=1m=n
x∈An,
x∈limAn=
∞?∞?
Am,
n,
x∈
m=n
∞?
Am,
m≥n,
n→∞n=1m=n
∞?∞?
Am.
2
9.(?1,1)(?∞,+∞)
?:(?1,1)→(?∞,+∞).x∈(?1,1),?(x)=tanπ
)21
2=(
1?z,y
(0,1)
R={r1,r2,···},???(0)=r1,???????(1)=r2,
?
[0,1]
(0,1)
???(rn)=rn+2,n=1,2,···??????(x)=x,x∈((0,1)\R),
16.
A
A
?n.A
A={x1,x2,···},A
?nA2n
17.
[0,1]
?A
?=A
n=1
∞?
?n={x1,x2,···,xn},AnA.A
?n,?AA
A
c.
[0,1]
A,[0,1]{r1,r2,···},
?√√?√B=,,···,,···?A
23n
?(?(
√
)=,2nn+1√
)=rn,
√
n=1,2,···n=1,2,···x∈B.
2n+1[0,1]
?(x)=x,
?xi
A
[0,1]A
c,c.Ai
A
c.
A={ax1x2x3···},
?i.
?
18.
c
A
E∞
xi∈Ai,Ai=c,i=1,2,···.
R
A?
ax1x2x3···∈A.?(ax1x2x3···)=(?1(x1),?2(x2),?3(x3),···).
i,?i(xi)=?i(x′i).
?i
′′?(ax1x2x3···)=?(ax′),1x2x3···′′ax1x2x3···=ax′.1x2x3···
xi=
x′i,
(a1,a2,···),
19.
xi∈Ai,
?i(xi)=ai.
(a1,a2,a3,···)∈E∞,ai∈R,i=1,2,···,
?
A
ax1x2x3···∈A,E∞
?(ax1x2···)=(?1(x1),?2(x2),···)=
?i
c.
n=1
∞?
An
c,
n0,
An0
c.
An<c,n=1,2,···.
E∞=c,
n=1
E∞
R
x=(x1,x2,···,xn,···)∈E∞,
∞?
An=E∞.
Pi
Pi(x)=xi.
A?i=Pi(Ai),i=1,2,···,
4
A?i,i<Ai<c,i=1,2,···.∞∞??ξ∈An.ξ∈An,ξi∈R\A?i,i,ξ=(ξi,ξ2,···,ξn,···)∈E∞.ξi=Pi(ξ)∈Pi(Ai)=A?i,
n=1
ξ∈R\A?iξ∈n=1
Ai0=c.
20.∞?n=1∈Ai,An=E∞,ξ∈E∞i0,01T,Tc.
T={{ξ1,ξ2,···}|ξi=0or1,i=1,2,···}.
TE∞?:{ξ1,ξ2,···}→{ξ2,ξ3,···},?TE∞?(T)x∈(0,1]
(0,1]TA≤E∞=c,(0,1]x=0.ξ1ξ2f((0,1])···,2ξi01,T≥(0,1]=c.
5f(x)={ξ1,ξ2,···},A=c.f
EoE′?E1.
P0P0∈E′P0U(P,δ)(P0)P1E(P1),P0U(P,δ)(P0)U(P,δ)?E.P0∈EoP0E.P1∈E∩U(P0)?E∩U(P,δ)
P0
E,P0∈E′,P0U(P,δ),P0U(P0)?U(P,δ),P1=P,P1P0P1P0E,P0U(P0)
P0P1P0∈E′.
U(P0)?U(P,δ)?E,P0∈Eo,U(P0)?E.P0∈U(P,δ)?E,
[0,1]P0∈Eo.2.E1E1R1′o?E1,E1,E1.′E1=[0,1],oE1=?,?1=[0,1].E
3.E2={(x,y)|x2+y2<1}.E2R2′o?E2,E2,E2.
′E2={(x,y)|x2+y2≤1},oE1={(x,y)|x2+y2<1},?1={(x,y)|x2+y2≤1}.E
4.E3
y=??sin1
?
(?∞,∞),|x?x0|<δx0∈E,f(x)>a,f(x0)>a.f(x)δ>0,x∈
x∈U(x0,δ)x∈E,U(x0,δ)?E,E
x0∈E,
9.xn∈E,Exn→x0(n→∞).f(xn)≥a,f(x)f(x0)=limf(xn)≥a,n→∞
F
y0∈F,d(x0,y0)=δ<?Gn=x|d(x,F)<11
n,n,
d(x0,F)=infd(x0,y)≥1
n).
?=1
∞x∈G
n?=1n,n,x∈Gn.n,x∈Gn,d(x,F)<11n??=U(x0,?)?Gn,y∈FGn
[0,1]
7
?
An,(?∞,0),(1,∞)
?
n=1
∞?
An∪(?∞,0)∪(1,∞).
?
[0,1]
7
11.
f(x)
[a,b]
c,
E={x|f(x)≥c}
E
E1
E1={x|f(x)≤c}
f(x)
[a,b]
8
E
E1
f(xn)≤f(x0)??0,
x0∈[a,b].f(x)
x0
c=f(x0)+?,
?0>0,xn→x0,f(xn)≥f(x0)+?0
x0∈E(f(x0)<f(x0)+?0=c),§2
E
f(x)
xn∈E={x|f(x)≥c},
[a,b]
12.
5:
E=?,E=Rn,
E
(
?E=?).
Pt=(ty1+(1?t)x1,ty2+Pt0∈?E.Pt∈E.
P0=(x1,x2,···,xn)∈E,P1=(y1,···,yn)∈E.
(1?t)x2,···,tyn+(1?t)xn),0≤t≤1.t0=sup{t|Pt∈E}.
t0,tn→t0
Pt0∈E.
Ptn∈E,
t0=1.
Ptn→Pt0,
t∈[0,1]
Pt0∈?E.
t0<t≤1,
tn,1>tn>
Pt0∈?E.
13.
Pt0∈E,
?E=?.
t0=0,tn,0<tn<t0,tn→t0,Ptn→Pt0,Ptn∈E,
P
1,
P
c.
??
n
2n?1
Ik
?
P3
11979
(n)
???
(
P),
=(0.1,0.2),=(0.01,0.02),=(0.21,0.22),
······
Ik,k=1,2,···,2n?1
(n)
=(0.a1a2···an?11,0.a1a2···an?12),
a1,a2,···,an?1
02.
[0,1]?P
1,
P
1,
x∈P,
x
x=
a1
32
+···+
an
ABφ:
∞?anφ:x=
n=12n·an
1.Em?E<+∞.
EIE?I.m?E≤m?I<+∞.2.
E={xi|i=1,2,···}.??>0,Ii,xi∈Ii,|Ii|=?
m?T=m?(T∩E)+m?(T∩?E),
E
6.
(Cantor)P
[0,1]
1
9,······3n
,
n
2n?1
=1(
).
m[0,1]=m(P∪([0,1]?P))=mP+m([0,1]?P).
mP=m[0,1]?m([0,1]?P)=1?1=0,
0.
7.
A,B?Rp
m?B<+∞.
A
m?(A∪B)=mA+m?B?m?(A∩B).
A
m?(A∪B)=m?((A∪B)∩A)+m?((A∪B)∩?A)=mA+m?(B?A).
m?B=m?(B∩A)+m?(B∩?A),
m?B<+∞,
m?(B∩?A)<+∞,
m?(B?A)=m?B?m?(A∩B),
m?(A∪B)=mA+m?B?m?(A∩B).
8.
E
?>0,
G
F,
F?E?G,
∞?
m(G?E)<?,m(E?F)<?.
mE<∞
?>0,G
i=1
mE+?,
∞?
|Ii|<mE+?.
G=E
i=1
mG?mE<?,
∞?
{Ii},i=1,2,···,mE≤mG≤
i=1∞?
i=1
Ii?E,
i=1∞?
Ii,
G?E,
mIi=
|Ii|<
m(G?E)<?.
mE=∞En
E=
n=1?
Gn,
Gn?En
m(Gn?En)<
∞?
En(mEn<∞),
i,n=1
∞?i,
m??∞?Bn?Bi,Bn?E?n=1∞?Bn?E?Bi?E.E?Ai,Bi?E?Bi?Ai,
n=1≤m?(Bi?E)≤m?(Bi?Ai)=m(Bi?Ai).
?i→∞,
n=1
10.∞?m(Bi?Ai)→0,m?BnE=n=1A,B?Rp,n=1∞?∞?Bn?E=0.?∞??Bn?Bn?E?n=1∞?Bn?EBnn=1
m?(A∪B)+m?(A∩B)≤m?A+m?B.
m?A=+∞
G2,m?B=+∞,m?A<+∞m?B<+∞GδG1G1?A,G2?B,mG1=m?A,mG2=m?B.
m?(A∪B)≤m(G1∪G2),m?(A∩B)≤m(G1∩G2).
m?(A∪B)+m?(A∩B)≤m(G1∪G2)+m(G1∩G2)=mG1+mG2=m?A+m?B.
11.E?Rp.?>0,F?E,m?(E?F)<?,
1En,Fn?E,m?(E?Fn)<
n.
m?(E?F)=0,E?F
E=F∪(E?F)
12.?
M,??M,?≤M.c
c,
?≥M,?=M.
3
1.
f(x)
E
r,
E[f>r]
E[f=r]
f(x)
E[f>a]=
n=1
∞?
r,E[f>r]
α,
E[f>rn],E[f>rn]
E[f>α]
{rn}
α
f(x)
E
r,E[f=r]
E[f>
√
x∈z,f(x)=
√
f(x)
E=(?∞,∞),z
(?∞,∞)
2,
r,E[f=r]=?
n→∞
E|fn?f|<
?
1
k,
x∈lim
k
?
.?
k
x∈
x∈
∞?
k=1
lim
k=1
?
k,
∞?
lim
?>0,
k0,,
k
.
1
k0
?
n→∞
|fn(x)?f(x)|<
?
E|fn?f|<
1
1
n→∞
E|fn?f|<
?
1
n→∞
fn(x)
n→∞
fn=+∞]
fn
+∞
E[
n→∞
limfn>lim
fn=+∞]?E[
limfn>lim
n→∞
n→∞
E[lim
n→∞
limfn=?∞]∪E[
n→∞
fn]
4.
E
[0,1]
f(x)=
f(x)
?
x,?x,
x∈E,x∈[0,1]?E.
[0,1]
|f(x)|
f(x)
0∈E,E[f≥0]=E
0∈E,[0,1]E0
E[f>0]=E
f(x)
x∈[0,1]
|f(x)|=x
|f(x)|
5.
fn(x)(n=1,2,···)?>0
E
a.e.
c
mE<∞.
E0?E,m(E\E0)<?,
|fn|a.e.
n
|fn(x)|≤c.
f.
f]∪(
n=0
∞?
E[|fn|=∞]),
n
E[|fn|=∞],E[fn→f]
mE1=0.
E?E1
fn(x)
n=0,1,2,···.
f(x).
E1=E[fn→
E2=E?E1,
x∈E2,sup|fn(x)|<∞.
E2=
∞?
k=1
E2[sup|fn|≤k],E2[sup|fn|≤k]?E2[sup|fn|≤k+1].
n
n
n
mE2=limmE2[sup|fn|≤k].
k→∞
n
k0
mE2?mE2[sup|fn|≤k0]<?.
n
E0=E2[sup|fn|≤k0],c=k0.
n
E0
n,|fn(x)|≤c,
m(E?E0)=m(E?E2)+m(E2?E0)<?.
6.
f(x)
(?∞,∞)
g(x)
[a,b]
f(g(x))
?∞,βn
E1=(?∞,∞),E2=[a,b].
∞?
E1[f>c]=(αn,βn),
n=1
f(x)
E1
c,E1[f<c]
(αn,βn)
(
αn
+∞).
E2[f(g)>c]=
n=1
g7.
E2
E2[g>αn],E2[g<βn]
∞?
E2[αn<g<βn]=
n=1
E[f(g)>c]
∞?
(E2[g>αn]∩E2[g<βn]),
fn(x),(n=1,2,···)fn(x)
E
”
”
f(x),
f.
{fn}a.e.
E
”
”
f(x),
δ>0,fn
Eδ?E,
m(E?Eδ)<δ
fna.e.
EδEδ
f(x).
E0).
E
mE0=0.
δ,E0?E?Eδ(fn(x)
fn
),
E
f(x)(
mE0≤m(E?E0)<δ,
δ→0,
2
8.
f(x)
E
δ>0,
f(x)
Eδ
m(E?Eδ)<δ,
f(x)
E
a.e.
Eδ?E
1/n,
En?E,
f(x)En
m(E?En)<
1
n.
n→∞,
mE0=0.E=(E?E0)∪E0=(
n=1∞?
n=1
a]∪(
En[f>a]),
f
En
∞?
En)∪E0=
n=0
En[f>a]
∞?
En.
a,E[f>a]=E0[f>
m?(E0[f>a])≤m?E0=0,
n=1
∞?
E0[f>a]En
E[f>a]
f
f
En
f(x)a.e.E
9.
f(x)≤g(x)
E
{fn}
f,
fn(x)≤g(x)a.e.fni(x)
E
E,n=1,2,···.
fn(x)?f(x),f(x)
fni(x)
En=E[fn>g].
{fni}?{fn},
E?
n=0
∞?
En
fni(x)≤g(x),fni(x)
f(x),
a.e.f(x).E0
∞∞??
mE0=0,mEn=0.m(En)≤mEn=0.
n=0n=0
f(x)=limfni(x)≤g(x)
E?
n=0
f(x)≤g(x)E
E
∞?
En
10.
fn(x)?f(x),
fn(x)≤fn+1(x)
n=1,2,···,
fn(x)
f(x).
fn(x)?f(x),
fni(x)
f(x)
En=E[fn<fn+1],m(
∞?
{fni}?{fn},
∞?
fni(x)
E
a.e.
f(x).
E0
mE0=0,mEn=0.
En)≤mEn=0
n=0n=0
E?
n=0
∞?
En
fni(x)
f(x),
fn(x)).
fn(x)En
f(x).(
n=0
fn(x)a.e.11.
f(x).
∞?
fn(x)
f(x),
E
fn(x)?f(x),fn(x)=gn(x)a.e.
n=1∞?
n=1,2,···,
gn(x)?f(x).
(
n=1
∞?
En=E[fn=gn]
m(En)≤
n=1
En)∪E[|f?fn|≥σ].
∞?
mEn=0.
σ>0,E[|f?gn|≥σ]?
mE[|f?gn|≥σ]≤m(
n=1
∞?
En)+mE[|f?fn|≥σ]=mE[|f?fn|≥σ].
3
fn(x)?f(x),12.
0≤limmE[|f?gn|≥σ]≤limmE[|f?fn|]≥σ=0
gn(x)?f(x).
mE<+∞,
E
fn(x)?f(x)
{fnk},
{fnk}
{fnkj},
j→∞
limfnkj(x)=f(x),a.e.
E.
{fn}
{fn(x)}
E
f(x).
η0>0,
{fnk},
{mE[|fn?f|≥η0]}
?0>0,
mE[|fnk?f|≥η0]>?0>0.
{fnk}
(1)
E
a.e.
f,
mE<+∞,
f(x)
E
fnkj?f(x),
(1)
{fnkj}
13.
mE<∞,g(x),
fn(x)
gn(x),n=1,2,···,
f(x)
(1)fn(x)gn(x)?f(x)g(x);(2)fn(x)+gn(x)?f(x)+g(x);
(3)min{fn(x),gn(x)}?min{f(x),g(x)};max{fn(x),gn(x)}?max{f(x),g(x)}.
(1)
f(x)a.e.
mE[|f|=∞]=0.
E[|f|≥n]?E[|f|≥n+1]
n=0
f|≥1]≤mE<∞,
∞?
E[|f|≥n]=E[|f|=∞],
E[|f|≥1]?E,mE[|
mE[|f|=∞]=limmE[|f|≥n]=0.
n→∞
n→∞
limmE[|g|≥n]=0.
?
5
5,mE[|
?>0,σ>0,
?
σ0=min
k,mE[|f|≥k]<
σ
?
fn?f|≥σ0]<
5
+
?
5
.
?σE|gnfn?gnf|≥
2(k+1)
?
?E[|gn|≥k+1]∪E[|fn?f|≥σ0].
?σmE|gnfn?gnf|≥
5
?
+
?
5
.
?σE|fgn?fg|≥
4
2(k+1)
?E[|f|≥k]∪E[|gn?g|≥σ0].
?σmE|fgn?fg|≥
?σ
E[|gnfn?gf|≥σ]?E|gnfn?gnf|≥
5
+
?
5?,
.
2?
?σ
mE[|gnfn?gf|≥σ]≤mE|gnfn?gnf|≥
2
<
3?
5
=?.
?>0,σ>0,
N,
n>N
mE[|gnfn?gf|≥σ]<?,
gnfn?gf.(2)
E[|(fn+gn)?(f+g)|≥σ]?E?|fσ
n?f|≥
2
?mE[|(fn+gn)?(f+g)|≥σ]≤mE?|fσ
n?f|≥
2limmE[|(f?,
n→∞
n+gn)?(f+g)|≥σ]≤nlim→∞
mE?|fσ
n?f|≥
fn+gn?f+g.(3)
fn?f,
|fn|?|f|.
E[|fn?f|≥σ]?E[||fn|?|f||≥σ].
nlim→∞
mE[||fn|?|f||≥σ]≤nlim→∞
mE[|fn?f|≥σ]=0,
|fn|?|f|.
fn?f,
a=0,afn?af.
E[|afn?af|≥σ]=E?
|fn?f|≥
σ
min{f(x)?g|a|
?
=0.
n(x),gn(x)}=
fn(x)+gn(x)?|fnn(x)|
(x)+g(x)?|f(x)?g(x)|
2
?
f2?.
min{fn(x),gn(x)}?min{f(x),g(x)}.max{fn(x),gn(x)}=fn(x)+gn(x)+|fn(x)?gn(x)|
1.
Lebesgue
Darboux
Darboux
f(x)
E
E
D:E1,E2,···,En,
1≤i≤n
maxmEi→0
S(D,f)→
??
f(x)dx,S(D,f)→
E
?
?
E
f(x)dx.
[0,1]
n,
[0,1]
?????1,f(x)=????0,
xx
[0,1][0,1]
,
?
n
→0(n→∞).
Dn={Ein},
n?
Ein=
n?i=1
?
i?1
n
.
?
n
,i=1,2,···,n?1,En=
n?1
S(D,f)=
n
i=1x∈Ei
sup
mEin
=
1·
1
3n
n(n=1,2,···),
f(x)
f(x)
En
P0
1
3n
,
?
f(x)dx=
[0,1]
∞??n=1
f(x)dx=
En
∞?n=1
nmEn=
∞?n=1
n·
2n?1
|f(x)|
?
?>0,
δ>0,
e?E
me<δ
e
|f(x)|dx<?.
δ>0,
N,
n>N
men<δ,n·men≤
?
en
|f(x)|dx<?.
limn·men=0.
n∞?
4.
mE<∞,f(x)
E
En=E[n?1≤f<n],
f(x)
E
?∞
|n|mEn<∞.
f(x)
E
|f(x)|
E
n≥1n≤0
EnEn
n?1≤|f(x)|=f(x)<n.
|n|≤|f|≤|n?1|=1?n,
?∞??∞?∞?∞????∞>|f(x)|dx=|f|dx+|f|dx≥(n?1)mEn+|n|mEn
E
=En
∞?n=1
|n|mEn+
n=1
?∞?n=0
En
n=0
En
n=1n=0
|n|mEn?
∞?n=1
mEn=
∞??∞
|n|mEn?
∞?n=1
mEn,
E
∞?n=1
∞?
mEn=m(
∞?n=1
En)≤mE<∞,
?∞
|n|mEn<∞.
?
?∞
∞?
|n|mEn,
∞??n=1∞?n=1
E
|f(x)|dx=
=
En
|f|dx+
|n|mEn+
n=0
?∞?n=0
?∞??
En
|f|dx≤
?∞?n=0
∞?n=1
nmEn+
∞??∞
?∞?n=0
|n?1|mEn
|n|mEn+
mEn≤|n|mEn+mE<∞.
|f(x)|5.
f+(x)R
f?(x)
f(x)=f+(x)?f?(x)),
f(x)
[a,b]R
(
f(x)
[a,b]
L
|f(x)|
[a,b]
(?
),
f(x)dx=(R)
[a,b]
?(
b
f(x)dx.),
0<?<b?a,f(x)4
a
f(x)
[a,b]
R?
[a+?,b]
R
|f(x)|
[a+?,b]
b
(R)
a+?
|f(x)|dx=
2
R?
§2
[a+?,b]
|f(x)|dx.
?→0,
(R)
?
b
a
|f(x)|dx=
?
[a,b]
|f(x)|dx.
f(x)
[a,b]?
L
|f(x)|
?
[a,b]§5
7,?
f(x)dx=f(x)dx?
+
?
f(x)dx=(R)
?
b
f(x)dx?(R)
+
?
b
f(x)dx=(R)
?
?
b
f(x)dx.
[a,b]
[a,b]
[a,b]a
a
6.
{fn}
E
nlim
→∞?
Efn(x)dx
=0,
fn(x)?0.
σ>0,
fn
σmE[|fn|≥σ]≤
?
fx)dx≤
.
E[|fn|≥σ]
n(?
fE
ndxmE[|fn|≥σ]≤
1
σ
?
f(x)dx=0.
E
nfn(x)?0.7.
mE<∞,{fn}
a.e.
n(x)|
nlim
→∞
?
|fE
1+|fn≥σ?E[|fn|≥σ],
limmE
?
|?
|fn|
1+|fn|
?0,
0≤
|fn|
1+|f=
n(x)|
dx?
0dx=0.
E
n→∞lim
?
E
|fn(x)|
1+|fn(x)|dx
?0.
1+|fn|
≥
σ
1+|fn|
≥
σ
x
a
y=
x
α≥1
?1
0|f(x)|dx≥?11x0|dx≥?1x|sin1
y|dy=∞,
α≥1
α<1f(x)L[0,1]1x|xα|,f(x)L
9.[0,1]nE1,E2,···,En,[0,1]nqq/n.?n?i(x)Ei[0,1]q?i=1i(x)≥q.mEi=?[0,1]?i(x)dx,
?n
mEi=
i=1?[0,1]?n?i(x)dx≥
i=1?qdx=q.[0,1]
Ei,mEi≥q
n?.
mE[f?0]≤n?∞=1mE?|f|≥1
?1+t=1.n
t∈(0,1)1
n?nt1t1√
?1
1+t=n2nt2+···?t1t2(n?1)<4[0,1]
?1?,t∈(0,1),
F(t)=?????????t
????
4√
t2
=6,
)
F(x)
(0,∞lim
dtn
?
(0,∞)
n
?n
t
1
?1+
t
dt=
n
?
dt
(0,∞)
1+x
=(1?x)+(x2?x3)+···,0<x<1,
ln2=1?
1
3
?
1
1
1+x
dx=
?∞?1
(x2n+1)dx=
=1?
1
n=0
?x2n?∞n=0
?2n+2
?
1+xdx
=ln2,
1
ln2=1?
3
?
1
?t
f(x,t)?????≤K,
a≤x≤b,|t?t0|<δ,
d
dt
?
b
f(x,t)dt=lim
1
a
n→∞
hn
?????=?????
ft′(x,t+θhn)·hn?
b
?
b
dt
f(x,t)dt=
lim
f(x,t+hn)?f(x,t)
a
an→∞
1?x
ln
1
(p+n)2(p>?1).
5
3
?
1
xp
x=(∞?xn)xpln1
x,
n=0
px∈(0,1)n+xln1
1?xln1
(n+p+1)2=?∞
n=1
(x)|dx≤K,
n→∞?E|fn
|f(x)|f(x)
16.f(x)[a??,b+?]
limt→0?ba|f(x+t)?f(x)|dx=0.
§41,σ>0,[a??,b+?]
?b+?
(x)??(x)|dx<σ
a??|f
3(b?a).
0<t<δx∈[a,b],
|?(x+t)??(t)|<σ
3+σ
3(b?a)·(b?a)=σ.
?b
limt→0a|f(x+t)?f(x)|dx=0.
61?(x),
17.
f(x),fn(x)(n=1,2,···)
E?
n→∞
lim
E
|fn(x)|dx=
??
n→∞
limfn(x)=f(x)a.e.
E,
E
|f(x)|dx,
e?E,
n→∞
lim
?e
|fn(x)|dx=
e
|f(x)|dx.
{fni(x)},
|f(x)?f(xn)|<
?0
?
e
|f(x)|dx=
?
lim
e
n→∞
?
|dx.
e
|fn(x)?
e
|f(x)|dx≥
nlim→∞
|fn(x)|dx,
ilim
→∞
?
e
|fni(x)|dx=
)|dx≥
n→∞
?
e
|fn(x?
e
|f(x)|dx≥
2
.
x∈(xn?δ,xn+δ)
2
≥
?0
2
?∞mEni=
δ?0=∞,
i=1
?∞i=1
7
|f(x)|
19.(0,∞)x→∞limf(x)=0.Rqf(x)Rp
Rpg(y)f(x)·g(y)Rp×Rqf(x)
g(y)RpRp×Rqf(x)g(y)Rp×RqRp×Rq
f(x),g(y)??
f(x),g(x)Rp×Rq§64,f(x)g(y)Rp×Rq????f(x)g(x)dxdy=dxf(x)g(y)dy=f(x)dx·g(y)dy<∞,RpRqRpRqf(x)=f+(x)?f?(x),g(y)=g+(y)?g?(y),f+(x),f?(x),g+(y),g?(y)f(x)g(y)=f+(x)g+(y)+f?(x)g?(y)?f?(x)g+(y)?f+(x)g?(y)
f(x)g(y)
20.D:?1≥x≥1,?1≥y≥1
??????f(x)=?????
?1xyxy(x2+y2)2dx
?1
(x2+y2)dx=2?1dx
?1?1xy?1
(x2+y2)2dx
?1xy
2y0?y
1.
(a,b)
f(x),g(x)
(a,b)
E
(a,b)
E
f(x)=g(x).xn∈E,
M
f(x)
N
g(x)
xn≤x0
x0∈M,
n→∞
limxn=x0,
f(x0+0)=f(x0)=f(x0?0).
E
(a,b)
f(x0?0)=limf(xn)=limg(xn)=g(x0?0).
n→∞
n→∞
f(x0+0)=g(x0+0),
x0
g(x)
N?M,
2.
M=N,
f(x)
g(x)
x0∈E,
M?N.
f(x)
{fn}[a,b]
b?
(fn)<K,(n=1,2,···),
fn(x)→f(x)(n→∞),
f(x)
a
[a,b]
T:a=x0<x1<···<xm=b,
m?i=1
b?
|fn(xi)?fn(xi?1)|≤(fn)<K,n=1,2,···.
am?i=1
m?i=1
|fn(xi)?fn(xi?1)|=lim
n→∞
|fn(xi)?fn(xi?1)|≤K.
f(x)3.
[a,b]
f(x)=xαsin
1
b?
(f)≤K.a
2
??1
?xαk?1sin
π
1
?
1
2
xβk
β
((n?1)?k)π+((n?1)?k)π+(n?k)π
+=2
π
+
?α
(n?k)π+
π
1
(n?k+1)π
1
k
.
k=2n?1
xβ?βxα?β?1cos1
tβ?xδ=xαsin1
T
v=
?n?f(a)|+
i)?f(xi?1)|
i=1
|f(xi)?f(xi?1)|=|f(x1)≤|f(x1)|+|f(a)|+
?b?ni=2
|f(x(f)≤2M+|f(b)|+|f(a)|,
x1
?
b(f)≤2M+|f(b)|+|f(a)|<∞,a
f(x)[a,b]6.
{fn}
[a,b]f(x)=
n=1
f(x)
[a,b]
?
∞fn(x)
n,
fn(x)
[a,b]
fn(x)=fn(a)+
?
x
f′
)dt.
a
n(tfn(x)
f′
n(x)≥0,a.e.
[a,b].
f(x)
[a,b]
f′(x)
[a,b]L
f(?
∞?
∞x)=
fn(x)=
fn(a)+
)dt.
n=1n=1
n?
∞=1
?x
f′
a
n(t?
∞?x
′
xfn(t)dt=
n=1
a
?
?
f′
)dt.
an(tn∞?
∞=1
fx)
n=1
n()]<∞.
n?
∞t)dt≤
fn(b)?fn(a=1
?b
f′
a
n(n?∞?
∞[=1
f′
n(x)
[a,b]
L
n=1
f(x)=
n(a)+
n?
∞f=1
?
∞xf′
n(t)dt
n=1
?a
[a,b]7.
f(x)
[a,b]
(1)f(x)[a,b]Lipschitz
(2)f(x)
[a,b]
(2)
(1).
x
f(x)=
?
g(t)dt,
a
3
a,b]
[
g(x)[a,b]|g(x)|≤K,x∈[a,b].[a,b]x′,x′′,x′>x′′,f(x)[a,b]Lipschitz
f(x)??′??x???′′′|f(x)?f(x)|=?g(t)dt?≤K|x′?x′′|,?x′′?(1)(2).[a,b]Lipschitz?x
f(x)=f(a)+f′(t)dt.f(x)[a,b]
a
x,y∈[a,b],
KLipschitz?????xy
g(x)[a,b]|f′(x)|≤K,a.e.??f′(x),g(x)=?K,??f′(t)dt??=|f(x)?f(y)|≤K|x?y|,[a,b].|f′(x)|≤K,|f′(x)|>K,
f(x)=f(0)+
8.?xg′(t)dt.0””S
””f(x),α(x)[a,b][a,b]
T:a=x0<x1<···<xn=b,
Mimif(x)[xi?1,xi]i=1,2,···,n,
S(T,f,α)=
s(T,f,α)=
??b
an?i=1n?i=1Mi(α(xi)?α(xi?1)),mi(α(xi)?α(xi?1)).f(x)dα(x)=infS(T,f,α),T
?
b
af(x)dα(x),f(x)α(x)S
”””
f(x)=”????0,???1,x∈?1,???1,x∈?2
4?12,1,?
α(x)=
????0,
[?1,1]
T:?1=x0<···<xi?1<?1
σ=
n?i=1
???1,
x∈?1,?
??
1
x∈?.
2
?
1
2
,1,
?
2
<xj<···<xn=1,
f(ξi)[α(xi)?α(xi?1)]=f(ξi)?f(ξj)
,
σ
?
1??1,ξ>?i?????
1
=0,ξi>?????????1,ξi<?1f(x)
22
ξi<?,
1
2
,
2
[?1,1]S
α(x)
S
”
”
f(x)
T:?1=x0<x1<···<xn=1,
?1
2
(xi?1,xi)
2
α(x0)=α(x1)=···=α(xn)=0.?1
2
S(T,f,α)=
0,s(T,f,α)=0;
?1
∈[xj?1,xj],
S(T,f,α)=
n?
Mk(α(xk)?α(xk?1))=1?1=0,
n?
k=1
s(T,f,α)=
??1f(x)dα(x)=?
?1
mk(α(xk)?α(xk?1))=0,
k=1
i=1
∞?
(ai,bi)?E,
∞?i=1
?
m?α(ai,bi)≥mα
?∞
?
(ai,bi)
i=1
?
≥m?αE,
inf
?
∞?i=1
m?α(ai,bi),
i=1
∞?
(ai,bi)?E
?
≥m?αE.
α(x)
α′(x).
x,
α(x?0)=α′(x?0),α(x+0)=α′(x+0),
???
∞?
∞?
?
m?α(ai,bi)=mα′(ai,bi).
E?R1,
m?αE=inf
=inf=inf=inf
m?α(ai,bi),
(ai,bi)?E
∞?
?
=m?α′E.
i=1
∞?i=1
i=1∞?
i=1∞?
i=1
?
(α(bi?0),α(ai+0)),
(ai,bi)?E
(α′(bi?0),α′(ai+0)),m?α′(ai,bi),
∞?
i=1
∞?
?
(ai,bi)?E?
i=1
?
(ai,bi)?E
i=1
L?S
L?S
α
L?S
L?S
L?S
α(x)
L?S
6