A function f that is not Riemann integrable but |f| is Riemann integrable?

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SUMMARY

The discussion centers on the concept of Riemann integrability, specifically examining whether a function can be non-Riemann integrable while its absolute value is Riemann integrable. The example provided is the function f defined as f(x)=1 for rational x and f(x)=-1 for irrational x on the interval [0,1]. This function is not Riemann integrable due to its discontinuity at every point in the interval. However, the absolute value function |f| equals 1 for all x in [0,1], which is Riemann integrable.

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MimuiSnoopy
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I was just going over Riemann integrability and how to prove it, and was just wondering is it possible to have a function f that is not Riemann integrable but |f| is Riemann integrable? Say on an interval [0,1] for example. (as that is what most examples I have done are on so easiest for me to compare)
How would this work? Or does it not?
 
Physics news on Phys.org
f(x)=1 for rational x
f(x)=-1 for irrational x

Is it Riemann integrable?
 

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