# I couldn't do this integral when I was 3... | Summary and Q&A

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December 4, 2019
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blackpenredpen
I couldn't do this integral when I was 3...

## TL;DR

Jesus discusses the integration of Ln(x) using a substitution method and introduces the concept of the polylogarithm function.

## Key Insights

• βΊοΈ Integration of Ln(1-x) can be approached using a substitution method and the polylogarithm function.
• π«° The polylogarithm function is defined as a series with two indices.
• β The polylogarithm function is connected to the Riemann zeta function when x=1.
• π«° The polylogarithm function has a notation of Li_s(x), where s represents the index and x represents the input.

## Transcript

but then was Jesus told I tried to integrate Ln of one month into the expired couldn't because I didn't have any special function for it but today I do so we'll see how to finish this right here of course we will take a used substitution let u equal to e to the X and we see that D U is equal to e to the X DX and DX is equal to tu over e to the X wh... Read More

### Q: How does Jesus approach the integration of Ln(1-x)?

Jesus uses a substitution method, setting u equal to e^x, and rewrites the integral as Ln(1-u). He then integrates Ln(1-u) using a power series expansion.

### Q: What is the polylogarithm function?

The polylogarithm function, denoted as Li_s(x), is defined as a series where the index n ranges from 1 to infinity. It is used to express integrals and has a connection to the Riemann zeta function.

### Q: How is the polylogarithm function related to the Riemann zeta function?

The polylogarithm function is related to the Riemann zeta function when x=1. When x=1, Li_s(x) equals the Riemann zeta function.

### Q: What is the connection between the polylogarithm function and the concept of the "best friend"?

L I_0(x) is equal to x times the "best friend" function. Jesus mentions that he will discuss this connection further in a future video.

## Summary & Key Takeaways

• Jesus demonstrates how to integrate Ln(1-x) using a substitution method and a power series expansion.

• He introduces the polylogarithm function, which is defined as a series with two indices, and discusses its connection to the Riemann zeta function.

• Jesus explains that the polylogarithm function can be used to express the integral of Ln(1-x) as a series.

• He concludes by mentioning that the polylogarithm function is connected to the concept of the best friend, and promises to discuss this further in the future.