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# logs -sorry 2 ask so many Qs!! watch

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1. hi ya!! im a little stuck with the last part, i cant see where 2 get the answer from.

i) y= log10x so that x= 10y

show x can be written in form eyln10. (can do that bit!)

ii)ans : dx/dy = ln10 eyln10

iii) hence show that the derivative of log10x withr espect to x is 1/(xln10).

hope that makes sense, thank u 4 help!!
2. You have dx/dy = ln10 eyln10, which you can re-write as:
dx/dy = ln10 eln(10^y)
= ln10 . 10^y
= ln10 . x

So:
d(log10x)/dx = dy/dx
= 1/(dx/dy)
= 1/(x ln10)

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Updated: June 3, 2005
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