RHIT MA113/Multiple Integral
Multiple Integral Edit
Evaluating Multiple Integrals Edit
Multiple Integrals are evaluated from the inside out, beginning by evaluating the innermost integral, then working outwards.
The inner integrals may have limits containing variables, so long as those variables are integrated in an enclosing integral. Because of this, the limits of outermost integrals must contain only constants.
Changing the Order of Integration Edit
So long as the order of integration is changed correctly, the multiple integral will cover the same region, and therefore order will not affect the end result of the multiple integral. In general, it is wise to begin by establishing the limits of the outermost integral first, then working inwards, to avoid any mistakes.
Converting Coordinate Systems Edit
Cartesian to Cylindrical Edit
Cartesian to Spherical Edit
Cylindrical to Spherical Edit
Uses Edit
Average Value Edit
The Average value of a function is equal to
Areas/Volumes Edit
The equation for Area is and Volume is
In Cartesian coordinates, and , therefore Area and Volume are and
The same process can be used in Polar, Cylindrical, and Spherical coordinates, as follows:
In Polar,
In Cylindrical,
In Spherical,
Masses Edit
The equation for the mass of an object is , where is the density of the object (which could be either a constant or function of position)
Moments Edit
First Moments Edit
, where r is the distance from the axis or line of rotation
Second Moments Edit
, where r is the distance from the axis or line of rotation