The quotient and product rule...

Adventure

okay , i just want to know is it alright to use the lnx(natural logx) way to prove the product/quotient rule from first principles. this is the method in the new concise maths book by George Humphrey.

it goes like this : For product rule : let y=uv


so lny=ln(uv) ===>> ln y = lnu + lnv

using implict differentiation 1/y . dy/dx = 1/u . du/dx + 1/v .dv/dx

sub back in uv for y and tidy up to get : dy/dx = v . du/dx + u . dv/dx



it's sooooo much handier than the f(x+h) way. I'm just not sure are u allowed to use it?

cian1500ww

Thats the way my teacher told us to do it. I'd say you should be fine.

Cokehead Mother

That isn't proving it from first principles.

boobookitty

Is this OL Maths?

The only way I'm aware of differentiating from first principles are the y+deltay or f(x+h) methods.

MaltEagle

For Ordinary Level, these forums are in the Log Books.

Timans

MaltEagle wrote: »

For Ordinary Level, these forums are in the Log Books.

:eek:

I can go on boards.ie through my log tables?

MaltEagle

Unless you have electronic log tables, I doubt it highly.