The Student Room Group

differentiating lnx

would differentiating xlnx give 1/x?

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

thanks
Reply 1
No, it's incorrect. Are you familiar with the product rule?
Reply 2
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...
no. :smile:

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
Reply 4
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:
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)
Reply 6
thanks all
Reply 7
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.
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 :biggrin:
:]
Reply 10
... over 2 year bump.
Reply 11
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:
exlnxe^{xlnx}
And differentiate using the product and chain rule.
Reply 12
anshul95
To differentiate x^x write it as:
exlnxe^{xlnx}
And differentiate using the product and chain rule.


or he can use the logarithmic differentiation
y=xxy=x^x
lny=xlnxlny=x\cdot lnx
differenciating both sides
1yy=lnx+1\frac{1}{y}y'=lnx+1
y=xx(lnx+1)y'=x^x(lnx+1)
Reply 13
@ztibor yes you could do that but I didn't know whether or not the person knew implicit
Reply 14
you should use Chain rule


:smile:
Original post by safety280
you should use Chain rule


:smile:

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. :biggrin:
Reply 16
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. :biggrin:


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


thanks :smile:
Reply 17
Original post by safety280

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


thanks :smile:

product rule actually.
Reply 18
Original post by anshul95
product rule actually.


yeah it's actually tomato tometo things :biggrin:

Quick Reply

Latest