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Constant, Sum, and Inequality Rules

The Constant, Sum, and Inequality Rules for double integrals follow easily from the corresponding rules for single integrals, using the Iterated Integral Theorem.

Constant Rule

12_multiple_integrals-110.gif

Sum Rule

12_multiple_integrals-111.gif

Inequality Rule

If f(x, y) ≤ g(x, y) for all (x, y) in D,

12_multiple_integrals-112.gif

PROOF

As an illustration we prove the Sum Rule.

12_multiple_integrals-113.gif

The Iterated Integral Theorem gives another proof that the area of D is equal to the double integral of 1 over D.

By definition of area between two curves,

12_multiple_integrals-114.gif

Using iterated integrals,

12_multiple_integrals-115.gif


Last Update: 2006-11-05