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I read from theoretical physics lecture notes the following: http://theory.physics.helsinki.fi/~fymmi/Luennot4_1-9.pdf

$$\Gamma(p)\Gamma(q)=4\int_0^\infty dr r^{2p+2q+1}e^{-r^2}\int_0^{\pi/2}d\varphi \cos^{2p-1}\varphi\sin^{2q-1}\varphi$$

Is it possible to put that dr just after the integral as I have understood that the function is in between the integral sing and dr?

notsure
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1 Answers1

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As long as it remains clear what is and is not being integrated, it should be fine.

Magres
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  • Okay. I thought somehow that, for example, $\int dr,r=\int 1 dr\cdot r=(r+C)r$ – notsure Jan 21 '15 at 01:47
  • As far as I know, it's just how physicists write things sometimes. I encountered it a lot in my physics classes when I was in undergrad. – Magres Jan 21 '15 at 02:08