What am i doing wrong? Log differentiation

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Homework Help Overview

The discussion revolves around using logarithmic differentiation to find the derivative of the function y = xln(x). Additionally, there is a separate problem involving the simplification of a derivative expression related to a different function.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants explore the process of logarithmic differentiation and question the steps taken in deriving the expressions. There is a focus on clarifying the transition between different forms of the derivative and the manipulation of terms.

Discussion Status

Participants are actively engaging with each other's attempts to clarify the differentiation process. Some have pointed out potential typos and are discussing the implications of these on the calculations. There is a collaborative effort to understand the reasoning behind each step, though no consensus has been reached on the final form of the derivative.

Contextual Notes

There are indications of confusion regarding the manipulation of terms and the application of logarithmic properties. Participants are working within the constraints of the homework problem without providing complete solutions.

A_Munk3y
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Homework Statement


Use logarithmic differentiation to find the derivative of the function.
y=xln(x)


also, if anyone could help me with this...
i have (for a diff problem) 1/(x2-1)1/2 * 1/2(x2-1)-1/2*2x
i know that is right, but i don't know how to get from that, to x/(x2-1)
i keep getting x/(x2-1)-1 because i thought that (x2-1)-1/2/(x2-1)1/2 = (x2-1)-1

The Attempt at a Solution



=> ln(y)=ln(xln(x))
=> ln(y)=ln(x)*ln(x)
1/y*y'=1/x*ln(x)+1/x*ln(x)
y'=1/x*ln(x)+1/x*ln(x)*xln(x)
 
Last edited:
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A_Munk3y said:
=> ln(y)=ln(xln(x))
=> ln(y)=ln(x)*ln(x)
1/y*y'=1/x*ln(x)+1/x*ln(x)
y'=1/x*ln(x)+1/x*ln(x)*xln(x)

Looks like you have a typo there with missing parentheses.

y'=(1/x*ln(x)+1/x*ln(x))*xln(x)

or y'=2*ln(x)*xln(x)-1
 
yea, i see the typo. Thanks for pointing that out, but

how did you get from the first equation to the 2nd?
where did the 1/x's go and how did you get xln(x)-1
 
A_Munk3y said:
how did you get from the first equation to the 2nd?
where did the 1/x's go and how did you get xln(x)-1

Oh, that is because 1/x=x-1 and then generally, xa*xb=xa+b.
 
Ahh! i see :)
Alright thanks for the help man!
I really appreciate it
 

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