# Thread: differentiate the cumulative Weibull equation

1. ## differentiate the cumulative Weibull equation

Cumulative WEibull equation is;

y= e(-(x/a)^b)

i.e. dy/dx =

2. .

3. Originally Posted by angusmdmclean
Cumulative WEibull equation is;

y= e(-(x/a)^b)

i.e. dy/dx =

$\frac{d}{dx} e^u = e^u \cdot \frac{du}{dx}$ where

$u = -\left(\frac{x}{a}\right)^b$

4. ## WEibull

I agree it is a fuction of a function but plee tell me tell me me what is the first derivative of the below equation i.e. du/dx

du/dt =

5. Originally Posted by angusmdmclean
I agree it is a fuction of a function but plee tell me tell me me what is the first derivative of the below equation i.e. du/dx

du/dt =
chain rule ...

$\frac{du}{dx} = -b\left(\frac{x}{a}\right)^{b-1} \cdot \frac{1}{a}$

6. ## Weibull function

BRILLIANT! THIS AGREES WITH WHAT I have seen published, but I COULD NOT RATIONALIZE IT. I HAVE FORGOTTON MY CALCULUS. My plan is to enter the Weibull equation (in the differenial form) into a program that has a diffeerential equation solver. I have data and I want the porgram to solve by best fitting the data.

I may have to enter the WEibill as 2 diff. equations.