# It's a Calculus Mistake | Summary and Q&A

7.4K views
November 1, 2022
by
The Math Sorcerer
It's a Calculus Mistake

## TL;DR

This video presents a proof that pi is equal to zero by rearranging terms in an alternating series, but it is a fake proof due to the inability to rearrange terms in non-absolutely convergent series.

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### Q: How does the proof claim that pi is equal to zero?

The proof rearranges terms in an infinite series and substitutes pi minus pi with zero, leading to the conclusion that zero equals pi. However, this is a fallacy due to the improper rearrangement of terms.

### Q: Why is it incorrect to rearrange terms in this series?

Rearranging terms is only allowed in absolutely convergent series. This series is not absolutely convergent, leading to the incorrect result of pi equaling zero when terms are rearranged.

### Q: What is the significance of absolute convergence?

Absolute convergence allows for rearrangement of terms in a series without changing the sum. If a series converges absolutely, it means that the sum of the absolute values of its terms converges.

### Q: How does the video explain the flaw in the proof?

The video explains that the series used in the proof, an alternating series with pi multiplied by negative one to the n, diverges. The terms oscillate between pi and negative pi, making the limit of the sequence indeterminate.

## Summary & Key Takeaways

• The video presents a step-by-step proof that claims pi is equal to zero by rearranging terms in an infinite series.

• The flaw in the proof lies in the incorrect assumption that terms can be rearranged without considering absolute convergence.

• Rearranging terms in a non-absolutely convergent series is not allowed in mathematics.