Equating integrands on two equal integrals?

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SUMMARY

The discussion centers on the validity of equating integrands from two integrals that yield the same value. Specifically, it addresses the integrals \(\int P(\theta,\phi)d\Omega = N\) and \(\int Q(\theta',\phi')d\Omega' = N\). The consensus is that even if both integrals equal the same constant \(N\), it is not valid to conclude that \(Q(\theta',\phi')d\Omega' = P(\theta,\phi)d\Omega\). This is illustrated with the example of two different functions, \(f(t)=t\) and \(f(t)=(1/2)\), both integrating to \(1/2\) over the interval from 0 to 1, reinforcing that equal integrals do not imply equal integrands.

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Homework Statement


This is more of a general question. If I have two different integrals that equal the same value, is it valid to equate the integrands?

Homework Equations


[tex]\int P(\theta,\phi)d\Omega = N[/tex]
[tex]\int Q(\theta',\phi')d\Omega' = N[/tex]
Where [tex]N[/tex] is a constant and [tex]d\Omega = sin\theta d\theta d\phi[/tex]

The Attempt at a Solution


Since it can be said:
[tex]\int Q(\theta',\phi')d\Omega' = N = \int P(\theta,\phi)d\Omega[/tex]

Is it valid to conclude that
[tex]Q(\theta',\phi')d\Omega' = N = P(\theta,\phi)d\Omega[/tex] ?

Thank you.
 
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The integral from 0 to 1 of f(t)=t dt is 1/2. The integral from 0 to 1 of f(t)=(1/2) dt is also 1/2. No, you can't equate the integrands.
 
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