0
$\begingroup$

I want to compute the area of a right trangle with base 2 and 3, but I want to test the truth of integration of the polar coordinate, so i decide to use this integration formula: $\int_{0}^{\arctan \frac{3}{2}} \int_0^{\frac{2}{\cos \theta}} r^2 r\;\mathrm{d}r\;\mathrm{d}\theta$ but with Wolfram Alpha's answer, I get a weird result which differs by 0.06... That make me suspect the truth of the polar coordinate.

  • 2
    Seems like a bit of an accusatory stance to take, to assume that your teachers (or the web, whatever the case may be) taught you something false. Perhaps you should phrase your question a bit more open-mindedly to the possibility that you made a mistake in your setup or computations.2011-12-12

1 Answers 1

3

Corrected: The area element doesn't have the $r^2$ in it, so the integral should be $\int_{0}^{\arctan \frac{3}{2}} \int_0^{\frac{2}{\cos \theta}} r\;dr\;d\theta$. Alpha says this is $3$.

  • 0
    @GerryMyerson: you are right. Either set of limits gives the same answer (as it should-it is just repositioning the triangle). I have updated the limits to match OP.2011-12-12