MHB Integration in polar coordinates

AI Thread Summary
The integral of the function (x^2+y^2)^(7/2) over the disk defined by x^2+y^2≤16 is evaluated using polar coordinates. The region D is described with 0≤θ≤2π and 0≤ρ≤4. The integral is expressed as I=∫_0^(2π)dθ∫_0^4(ρ^2)^(7/2)ρ dρ. The calculation results in I=2π[(ρ^9)/9] evaluated from 0 to 4, yielding a final result of (2^19)π/9. This demonstrates the effectiveness of polar coordinates in simplifying the evaluation of double integrals over circular regions.
Fernando Revilla
Gold Member
MHB
Messages
631
Reaction score
0
I quote a question from Yahoo! Answers

By changing to polar coordinates, evaluate the integral.
(Integrand)(integrand)[(x^2+y^2)^(7/2)… where D is the disk x^2+y^2<=16.

I have given a link to the topic there so the OP can see my response.
 
Mathematics news on Phys.org
Denote $I=\displaystyle\iint_{D}(x^2+y^2)^{7/2}dxdy$ wiith $D\equiv x^2+y^2\le 16$. We have: $D\equiv \left \{ \begin{matrix}0\le \theta\le 2\pi\\0\le \rho \le 4\end{matrix}\right.$, so $$I=\int_0^{2\pi}d\theta\int_0^4(\rho^2)^{7/2}\rho d\rho=2\pi \left[\frac{\rho^9}{9}\right]_0^4=\frac{2^{19}\pi}{9}$$
 
Suppose ,instead of the usual x,y coordinate system with an I basis vector along the x -axis and a corresponding j basis vector along the y-axis we instead have a different pair of basis vectors ,call them e and f along their respective axes. I have seen that this is an important subject in maths My question is what physical applications does such a model apply to? I am asking here because I have devoted quite a lot of time in the past to understanding convectors and the dual...
Insights auto threads is broken atm, so I'm manually creating these for new Insight articles. In Dirac’s Principles of Quantum Mechanics published in 1930 he introduced a “convenient notation” he referred to as a “delta function” which he treated as a continuum analog to the discrete Kronecker delta. The Kronecker delta is simply the indexed components of the identity operator in matrix algebra Source: https://www.physicsforums.com/insights/what-exactly-is-diracs-delta-function/ by...
Back
Top