What am i doing wrong? Log differentiation

In summary, the conversation discusses using logarithmic differentiation to find the derivative of the function y=xln(x). The attempted solution involves using the logarithmic properties and simplifying the equation to get the derivative. The individual asking for help also has a typo in their solution, which is pointed out by the other person. They then ask for clarification on how to get from the first equation to the second, which involves applying the power rule and simplifying the exponent.
  • #1
A_Munk3y
72
0

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:
Physics news on Phys.org
  • #2
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
 
  • #3
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
 
  • #4
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.
 
  • #5
Ahh! i see :)
Alright thanks for the help man!
I really appreciate it
 

Related to What am i doing wrong? Log differentiation

1. What is log differentiation?

Log differentiation is a mathematical technique used to find the derivative of a function that contains logarithmic terms. It involves taking the natural logarithm of both sides of the function, then using the properties of logarithms to simplify and differentiate the function.

2. Why do we use log differentiation?

Log differentiation is useful when taking the derivative of a function that contains logarithmic terms. It allows us to simplify the function and make it easier to differentiate, especially when the function is complex or involves multiple logarithmic terms.

3. What are the steps to perform log differentiation?

The steps to perform log differentiation are:

1. Take the natural logarithm of both sides of the function.

2. Use the properties of logarithms to simplify the function.

3. Differentiate the function using the power rule and chain rule.

4. Rewrite the function in its original form, without the natural logarithm.

4. Can log differentiation be used for any function?

No, log differentiation can only be used for functions that contain logarithmic terms. It is not applicable to other types of functions.

5. What are some common mistakes when performing log differentiation?

Some common mistakes when performing log differentiation include:

- Forgetting to take the natural logarithm of both sides of the function.

- Incorrectly applying the properties of logarithms.

- Forgetting to use the chain rule when differentiating the function.

- Not rewriting the function in its original form after differentiation.

Similar threads

  • Calculus and Beyond Homework Help
Replies
5
Views
352
  • Calculus and Beyond Homework Help
Replies
2
Views
614
  • Calculus and Beyond Homework Help
Replies
6
Views
600
  • Calculus and Beyond Homework Help
Replies
3
Views
410
  • Calculus and Beyond Homework Help
Replies
4
Views
765
  • Calculus and Beyond Homework Help
Replies
5
Views
569
  • Calculus and Beyond Homework Help
Replies
12
Views
1K
  • Calculus and Beyond Homework Help
Replies
8
Views
1K
Replies
5
Views
1K
  • Calculus and Beyond Homework Help
Replies
8
Views
802
Back
Top