Search results
Results from the WOW.Com Content Network
This amounts to finding an area of a region by first comparing it to the area of a second region, which can be "exhausted" so that its area becomes arbitrarily close to the true area. The proof involves assuming that the true area is greater than the second area, proving that assertion false, assuming it is less than the second area, then ...
and conversely the latter equality implies the former by standard techniques in Lebesgue integration. More generally, the coarea formula can be applied to Lipschitz functions u defined in Ω ⊂ R n , {\displaystyle \Omega \subset \mathbb {R} ^{n},} taking on values in R k {\displaystyle \mathbb {R} ^{k}} where k ≤ n .
Example of a domain transformation from cartesian to polar. Example 2c. The domain is D = {x 2 + y 2 ≤ 4}, that is a circumference of radius 2; it's evident that the covered angle is the circle angle, so φ varies from 0 to 2 π, while the crown radius varies from 0 to 2 (the crown with the inside radius null is just a circle). Example 2d.
Abramowitz, Milton; Stegun, Irene A., eds. (1972). "Chapter 3". Handbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables.
The integral as the area of a region under a curve. A sequence of Riemann sums over a regular partition of an interval. The number on top is the total area of the rectangles, which converges to the integral of the function. The partition does not need to be regular, as shown here.
For example, suppose we want to find the integral ∫ 0 ∞ x 2 e − 3 x d x . {\displaystyle \int _{0}^{\infty }x^{2}e^{-3x}\,dx.} Since this is a product of two functions that are simple to integrate separately, repeated integration by parts is certainly one way to evaluate it.
Limits of integration can also be defined for improper integrals, with the limits of integration of both + and again being a and b. For an improper integral ∫ a ∞ f ( x ) d x {\displaystyle \int _{a}^{\infty }f(x)\,dx} or ∫ − ∞ b f ( x ) d x {\displaystyle \int _{-\infty }^{b}f(x)\,dx} the limits of integration are a and ∞, or − ...
The term "quadrature" is a traditional term for area; the integral is geometrically interpreted as the area under the curve y = x n. Traditionally important cases are y = x 2 , the quadrature of the parabola , known in antiquity, and y = 1/ x , the quadrature of the hyperbola , whose value is a logarithm .