Recent content by smath42

ah ok :-D I was trying to see how one could find h'g+hg' from f'(g)*g' "only"

I'm sorry I must have a very slow mind today but I don't see exactly why the implication and the second equality.

hum ok I can now do f'(y) = h(g^{-1}(y)) + yg^{-1}'(y)h'(g^{-1}(y)) = h(x) + yh'(g^{-1}(y))/g'(g^{-1}(y)) then g'df/dy = g'h+hg' ok... thanks !

Could you guys explain me what is f here please. I don't know why but I really have trouble seing where is the composition here

hum... then here too, I can't find what l is although I see l(g(x)) should be h(x)

OK I see that now, but I'm still in trouble to calculate df/dg. I'd like to say f(u) = h(x)*u but then again I end up with h(x) for df/dg

are there 2 f ? the one if f(x) = h(x)*g(x) and the one if f(g(x)) ?

humm... so you've seen where my problem is... what's f ?

that's where I'm confused... my first thought that in f(g(x)) f(y) is the function that multiplies y by h(x). therefore if I derivate with respect to y, I get h(x). Which apparently is wrong... no your question replaces x by y, which in fact doesn't really change anything so I'd say f(y)...

Here is a simple question : let f(g(x)) = h(x)*g(x). I want to calculate df/dx. If I use the product rule, I get g(x)h'(x) + h(x)g'x). Now if I use the composition/chain rule, I get df/dx = df/dg * dg/dx = h(x) * g'(x) which is different. I guess my df/dg = h is wrong, but I can't see what...