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Theorems on multiple integration

1)    To with it is limited ž

To its frontier is measurable   > is measurable and has measure 0

 

2)    If I have a continuous function on compact a measurable T ž

its diagram is with limited and measurable and has null measure.

The function is continuous on a compact one therefore for Heine - Cantor is also uniform continuous that it implies that if I take w' and w' ' ? T such che || w' - w' ' || < d then is had che || f(w') - f(w' ') || < and.

A regular decomposition (of diametro is carried out < d) of a rectangle which it contains the T dominion.

For Bolzano Weierstrass (If and  "n it is a closed entirety and limited ž Max(E) and Min(E) exist)

on everyone of the T the will exist the maximum and the minimum of the function, and an interval of is created "with 3 height comprised between the minimum and the maximum assumed from the function on spaces out. Therefore the measure of the surface is given from the sum of the measures of these 3 intervals of " that is < and in how much the function is continuous on a compact one therefore for Heine - Cantor is also uniform continuous that it implies that if I take w' and w' ' ? T such that || w' - w' ' || < d then is had che || f(w') - f(w' ') || < and.

3) the cilindroide is with measurable:

Enough to demonstrate that a its frontier has null three-dimensional measure therefore it is in fact up for the f(x, y) for the previous theorem and therefore is for the base in how much has height 0 like pure for the sidewall, both in fact can be enclosed in a plurirettangolo of "3 of infinitesimal measure.

 

4) If I have one constant function compact L on a measurable one of T base? "2 and therefore D is the cilindroide of T base, is had :

It is supposed that the base is contained in plurintervallo P2 and contains plurintervallo the Pthat is 1 P1 ? T ? P2 therefore has m(P1) < m(T) < m(P2), of the L rest is constant therefore Lm(P1) < Lm(T) < Lm(P2) with Lm(T) = m(D) is had therefore

|m(D) - Lm(t)| < L |m(P2) - m(P1)| £ L and in how much for the theorem of Heine Cantor if f it is continuous on a compact one then f are uniform continuous and therefore if the distance between the two points of the dominion is < d žthe distance between the images he is smaller of and .

 

5) If I have a continuous function on compact a measurable T? "2 and therefore D is the cilindroide of T base, is had :

For the theorem of Heine Cantor being the continuous function on a compact one is also uniform continuous therefore choosing a smaller amplitude of d for the regular decomposition of the T dominion will obtain one distance between the images smaller of and .

to)    sTo,p = is comprised between the sum of Cauchy that uses the minimum of the function on every floor tile of the regular decomposition and the measure of Cauchy that instead employs the maximum.

b)    the measure of the cilindroide S m(Di) is comprised between the measure of the cilindroide that uses the maximum value of the f on every floor tile and the measure of the cilindroide that uses the minimal value of the f on every floor tile.

They give a) and b) dato that the difference between maximum and minimum is on every smaller floor tile of and then is had che | sTo,p - l | < and in fact

 

6) Formula of reduction for double integrals:

If f it is continuous on simple a T dominion regarding axis x ž

Single geometric interpretation

 

7) Formula of reduction for triple integrals by means of integration for threads:

If f it is continuous on simple a T dominion regarding the plan xy ž

Single geometric interpretation

 

8) Formula of reduction for triple integrals by means of integration for sections:

If it is had to < x < b and the sections of D with an orthogonal plan to axis x are measurable then are had :

Single geometric interpretation

 

9) Formula for the change of variable:

If To he is compact a measurable one having like T image and r(u, v) it is a biiezione whose jacobiano is not null ž

Single geometric interpretation

 

10) Theorem Guldino Bread:

The volume of the solid S that is obtained from a complete spin around to the axis z of contained limited and measurable a T entirety in plan x = 0 is given from the formula  being the coordinate of the centroide.

It is obtained passing in polar coordinates and remembering the definition of baricentro .