Join TSR now and get all your revision questions answeredSign up now

differentiating lnx Watch

    • Thread Starter
    Offline

    0
    ReputationRep:
    would differentiating xlnx give 1/x?

    the lnx part gives 1/x and the x 1 so is that correct?

    thanks
    Offline

    2
    No, it's incorrect. Are you familiar with the product rule?
    Offline

    2
    ReputationRep:
    Product rule: x(lnx)' + x'(lnx)=1+lnx

    So, what you said in yuor first line is wrong, but the second line is kind of correct...
    Offline

    1
    ReputationRep:
    no.

    product rule

    differentiating a product uv = v(du/dx) + u(dv/dx)

    u = x

    v = lnx

    therefore differentiating xlnx = lnx(1) + x(1/x) = lnx + 1
    Offline

    2
    ReputationRep:
    No it won't.

    Using product rule, it becomes [ x * 1/x ] + [ 1/x ] or in other words, 1/x + 1.

    Edit: Holy ****, this forum is full of mathematical hawks.

    OP torn to pieces :eek:
    Offline

    1
    ReputationRep:
    (Original post by sdt)
    No it won't.

    Using product rule, it becomes [ x * 1/x ] + [ 1/x ] or in other words, 1/x + 1.

    Edit: Holy ****, this forum is full of mathematical hawks.

    OP torn to pieces :eek:
    don't you mean lnx? ^^

    (post farming ftw)
    • Thread Starter
    Offline

    0
    ReputationRep:
    thanks all
    Offline

    2
    ReputationRep:
    (Original post by amjw)
    don't you mean lnx? ^^

    (post farming ftw)

    Doh! Yes indeed. I went over this about 30 times trying to differentiate x^x. Maybe I'm mathematically challenged :rolleyes:

    Not post farming, I didn't even realise what I wrote.
    Offline

    1
    ReputationRep:
    (Original post by sdt)
    Doh! Yes indeed. I went over this about 30 times trying to differentiate x^x. Maybe I'm mathematically challenged :rolleyes:

    Not post farming, I didn't even realise what I wrote.
    i meant me
    Offline

    0
    ReputationRep:
    :]
    Offline

    3
    ReputationRep:
    ... over 2 year bump.
    Offline

    2
    ReputationRep:
    Doh! Yes indeed. I went over this about 30 times trying to differentiate x^x. Maybe I'm mathematically challenged
    To differentiate x^x write it as:
    e^{xlnx}
    And differentiate using the product and chain rule.
    Offline

    3
    ReputationRep:
    (Original post by anshul95)
    To differentiate x^x write it as:
    e^{xlnx}
    And differentiate using the product and chain rule.
    or he can use the logarithmic differentiation
    y=x^x
    lny=x\cdot lnx
    differenciating both sides
    \frac{1}{y}y'=lnx+1
    y'=x^x(lnx+1)
    Offline

    2
    ReputationRep:
    @ztibor yes you could do that but I didn't know whether or not the person knew implicit
    Offline

    0
    ReputationRep:
    you should use Chain rule

    Offline

    3
    ReputationRep:
    (Original post by safety280)
    you should use Chain rule

    You waited 6 months after the almost-three-years-old thread had died to post something which isn't even correct (or is too vague to be used in any sensible way)... :p:

    Oh, and welcome to TSR.
    Offline

    0
    ReputationRep:
    (Original post by Farhan.Hanif93)
    You waited 6 months after the almost-three-years-old thread had died to post something which isn't even correct (or is too vague to be used in any sensible way)... :p:

    Oh, and welcome to TSR.

    hey, first, I was googling that function then I got a link for this thread , chain rule in this case is perfectly applied and sensible.


    thanks
    Offline

    2
    ReputationRep:
    (Original post by safety280)

    hey, first, I was googling that function then I got a link for this thread , chain rule in this case is perfectly applied and sensible.


    thanks
    product rule actually.
    Offline

    0
    ReputationRep:
    (Original post by anshul95)
    product rule actually.
    yeah it's actually tomato tometo things
 
 
 
Poll
Is GoT overrated?
Useful resources

Make your revision easier

Maths

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

Equations

How to use LaTex

Writing equations the easy way

Student revising

Study habits of A* students

Top tips from students who have already aced their exams

Study Planner

Create your own Study Planner

Never miss a deadline again

Polling station sign

Thinking about a maths degree?

Chat with other maths applicants

Can you help? Study help unanswered threads

Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Quick reply
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.