# Feynman technique: integral of (x-1)/ln(x) from 0 to 1 | Summary and Q&A

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October 1, 2017
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Feynman technique: integral of (x-1)/ln(x) from 0 to 1

## TL;DR

This video explores an advanced integration technique that does not involve power series, focusing on how to integrate functions with ln x in the denominator.

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### Q: How does differentiating exponential functions help eliminate ln x in the integration process?

Differentiating exponential functions of ln x produces ln x as a factor, which is needed to eliminate ln x from the integral. The technique involves treating x as a constant and introducing a parameter to differentiate with respect to.

### Q: What is the name of the integration technique used in the video?

The integration technique used in the video is called the "finiteness technique."

### Q: How is the integral from 0 to 1 x to the b power and minus 1 over ln x defined as a function of b?

The integral from 0 to 1 x to the b power and minus 1 over ln x is defined as a function of b, denoted as i of b.

### Q: How is i of b differentiated with respect to b?

To differentiate i of b with respect to b, the video uses the differentiation under the integral sign technique, resulting in a derivative of 1 over b + 1.

### Q: What is the value of i prime of b when b is equal to 1?

When b is equal to 1, i prime of b is equal to 1 over 1 + 1, which simplifies to 1/2.

### Q: How is i of b obtained by integrating i prime of b with respect to b?

To obtain i of b from i prime of b, both sides of the equation are integrated with respect to b, resulting in the integral of 1 over b + 1, which evaluates to ln absolute value of b + 1.

### Q: What is the value of i of 1?

By substituting b with 1 in the expression for i of b, we get ln of 1 + 1, which simplifies to ln 2.

## Summary & Key Takeaways

• The video introduces a new integration technique for functions with ln x in the denominator, without using power series.

• The technique involves differentiating exponential functions of ln x to produce ln x, and treating x as a constant by introducing a parameter.

• By defining a new function and differentiating it with respect to the parameter, the video demonstrates how to integrate the original function.