.
1.f(x)>=0 "xÎ[a,b], aòbf(x)dx=S
2.S=aòcf(x)dx+còbf(x)dx=aòbf(x)dx
3.S=aòbf2(x)-aòbf1(x)dx=aòb[f2(x)-f1(x)]dx
4. :
Y=f1(x)
Y=f2(x)
5.S=aòb[f2(x)+|AB|-f1(x)-|AB|]dx=aòb[f2(x)-f1(x)]dx
.
y=f(x) [a;b], f(x)- [a;b]. .
.
n . :a=x0<x1<..<xi-1<xi<..<xn=b
[Mi-1Mi] :∆li=Ö(xi-xi-1)2+(yi-yi-1)2=Ö∆x2i-∆y2i=Ö1+(∆yi/∆xi)2∆xi
:
L= i
l sf(fi;x) : ∆y=f/(x;∆x)
∆yi/∆xi=f/(xi)=y/(xi)n, xiÎ[xi-1;xi]
L=s(fi,xi)= i
l-max∆x
L= i
L=aòbÖ1+(y/)2dx,y=y(x) y=f(x)
:
x=x(t),y=y(t), tÎ[t1,t2]
x=x(t) x=a,t=t1
dx=x/(t)dt x=b,t=t2
y/=y/t/x/t
:
l=aòbÖ1+(y/x)dx=aòbÖ1+(y/t)2/(x/t)2*x/tdt=
=t1òt2Ö((x/t)2+(y/t))/x/t*x/tdt=t1òt2Ö(x/t)2+
+(y/t)2
l=t1òt2Ö(x/t)2+(y/t)2dt, x=x(t)
y=y(t),tÎ[t1,t2]
:
l=t1òt2Ö(x/t)2+(y/t)2dt, x=x(t)
y=y(t),tÎ[t1,t2]
, :
: x=rcosj
y=rsinj
, :r=r(j),α£j<β
, , t=j, l=αòβÖ(x/j)2+(y/j)2dj
x y : x=r(j)cosj
y=r(j)sinj
x/j=r/(j)cosj-r(j)sinj
y/j=r/(j)sinj+r(j)cosj
(x/j)2=(r/cosj-rsinj)2=(r/)2cos2j- 2r/cosjsinj+sin2j*r2
+ (y/j)2=(r/sinj-rcosj)2=(r/)2sin2j-2r/sinjcosj+cos2j*r2
(x/j)2+(y/j)2=(r/)2+r2, :
l=αòβÖ(r/)2+r2dj, r=r(j)
jÎ[α;β]
.
y=y(x), dl=Ö1+(y/)2dx
x=x(t)
y=y(t) ` dl=Ö(x/t)2+(y/t)2dt
x=x(t)
y=y(y)
z=z(t) dl=Ö(x/t)2+(y/t)2+(z/t)2dt
r=r(j), dl=Ö(r/)2+r2dj
.
x=a x=b , Î[a;b] S(x):
1. [a;b] n
2. ∆i xiÎ∆i
3. xi x=xi^OX S(xi)
4. ∆I , ∆Vi=S(xi)*∆xi
|
|
s=(S, xi)= =
V=aòbS(x)dx
: ,.. , y=y(x) a£x£b
S(x)=py2(x)
V=paòby2(x)dx
.
I f(x,y) Di, e>0 d(e)>0, .D , l<d(e), x, :
|s(f,x)-I|<e
: òDòf(x,y)dS=òDòf(x,y)dxdy=I
:I=
- :
1.: - af1(x,y)+bf2(x,y) .D,
òDò(af1(x,y)+bf2(x,y))dS=aòDòf1(x,y)dS+bòDòf2(x,y)dS, a b-.
2. : D=D1ÈD2,D1Ç=Æ,
òDòf(x,y)dS=òD1òf(x,y)dS+òD2òf(x,y)dS
3. "(x,y)ÎD,f1(x,y)≥f2(x,y),
òDòf1(x,y)dS≥òDòf2(x,y)dS
4.| òDòf(x,y)dS|£òDò|f(x,y)dS
5. : f(x,y)- D, MÎD,
òDòf(x,y)dS=f(M)S, S- D