How to welcome a math Phd friend at the airport @blackpenredpen
How to welcome a math Phd friend at the airport  @blackpenredpen
Uploaded December 2025 | Updated September 2026, 2 weeks ago
Dr Peyam is visiting Taiwan and this is how I welcomed him! @drpeyam
We will investigate if the function f, defined from Q to R, such that f(x)=1 if x^2 is greater than 2 and f(x)=0 if x^2 is less than 2, is continuous or not. At first you might think f is discontinuous since there are jumps at x=+-sqrt(2), but we have to watch out for the domain! Such a classic real analysis question: Source: reddit.com/r/askmath/s/cy1aeuquja

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How to welcome a math Phd friend at the airport

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