# I can't understand the fact

• I
I can's understand the fact about the equation

i cant prove the equation from the first attachment to the second attachment pls help.

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andrewkirk
Homework Helper
Gold Member
The second last formula is ##\frac{dx}{dy}\frac d{dx}\left(\frac{dy}{dx}\right)^{-1}##.
If we write ##y'## for ##\frac{dy}{dx}## then that is
$$\frac1{y'}\frac d{dx}\left(\frac 1{y'}\right)$$
What happens when you perform the differentiation?

funlord
Thank you very much, I can understand now why it has a negative sign