RHIT MA113/Multiple Integral
Multiple IntegralEdit
Evaluating Multiple IntegralsEdit
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 IntegrationEdit
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 SystemsEdit
Cartesian to CylindricalEdit
Cartesian to SphericalEdit
Cylindrical to SphericalEdit
UsesEdit
Average ValueEdit
The Average value of a function is equal to
Areas/VolumesEdit
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,
MassesEdit
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)
MomentsEdit
First MomentsEdit
, where r is the distance from the axis or line of rotation
Second MomentsEdit
, where r is the distance from the axis or line of rotation