What is the Integral of 1 over 2 to the Natural Log of X?

Click For Summary

Discussion Overview

The discussion revolves around the integral of the function \( \frac{1}{{2}^{\ln x}} \). Participants explore different methods for solving this integral, including u-substitution and transformations involving logarithmic and exponential functions.

Discussion Character

  • Mathematical reasoning, Homework-related

Main Points Raised

  • One participant proposes using the substitution \( u = {2}^{\ln x} \) and derives \( u = x^{\ln 2} \), but expresses uncertainty about the next steps.
  • Another participant suggests a different substitution \( u = \ln(x) \), leading to the integral \( I = \int \left(\frac{e}{2}\right)^u \, du \), and provides a method to finish the integration.
  • A later reply reiterates the substitution \( u = \ln(x) \) and confirms the resulting expression for the integral, questioning if it simplifies to \( \frac{{(\frac{e}{2})}^{\ln x}}{\ln(\frac{e}{2})} + C \).
  • One participant agrees with the last expression, indicating it appears correct.

Areas of Agreement / Disagreement

There is some agreement on the validity of the substitution methods and the resulting expressions, but the discussion does not reach a consensus on the best approach or final form of the integral.

Contextual Notes

Participants do not clarify all assumptions involved in their substitutions, and the discussion does not resolve the potential complexities of the integral or the implications of the transformations used.

tmt1
Messages
230
Reaction score
0
I have this integral

$$\int_{}^{}\frac{1}{{2}^{lnx}} \,dx$$

I'm not sure the best way to do it.

I tried u-substitution:

$u = {2}^{lnx}$ and thus $u = {x}^{ln2}$, therefore $du = ln2({n}^{ln2 - 1}) dx$. However, not sure how to proceed from there.
 
Physics news on Phys.org
I would let:

$$u=\ln(x)\implies dx=e^u\,du$$

And you now have:

$$I=\int\left(\frac{e}{2}\right)^u\,du$$

Now, use the fact that:

$$\frac{d}{dv}\left(\frac{a^v}{\ln(a)}\right)=a^v$$

to finish. :)
 
MarkFL said:
I would let:

$$u=\ln(x)\implies dx=e^u\,du$$

And you now have:

$$I=\int\left(\frac{e}{2}\right)^u\,du$$

Now, use the fact that:

$$\frac{d}{dv}\left(\frac{a^v}{\ln(a)}\right)=a^v$$

to finish. :)

So it would be $$\frac{{(\frac{e}{2})}^{lnx}}{ln(\frac{e}{2})} +C$$?
 
Yes, looks correct to me. :D
 

Similar threads

Replies
8
Views
4K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 14 ·
Replies
14
Views
3K
  • · Replies 15 ·
Replies
15
Views
4K
  • · Replies 27 ·
Replies
27
Views
2K
  • · Replies 2 ·
Replies
2
Views
1K