Ask Your Question
2

Formal implicit differentiation

asked 2020-04-24 11:41:04 -0600

Cyrille gravatar image

updated 2020-04-27 02:32:34 -0600

As my question was poorly asked, I rewrite it.

I was searching for the code of first order and second order differentiation of an implicit function. Finally I found and post it.

edit retag flag offensive close merge delete

1 answer

Sort by » oldest newest most voted
1

answered 2020-04-25 02:54:34 -0600

Cyrille gravatar image

updated 2020-12-03 08:00:03 -0600

Here is the code for first and second order implicit differentiation of a two variables function

  #Evaluation of the two first derivatives of an implicit function
var("x, y, dx, dy, al, be")
V=function('V')(x, y)# A) either A or B should be uncomment
#V= x^al*y^be# B)
V_x = diff(V, x)
V_y = diff(V, y)
#Evaluation of the two first derivatives of an implicit function
var("x, y, dx, dy, al, be")
V=function('V')(x, y)# A) either A or B should be uncomment
#V= x^al*y^be# B)
V_x = diff(V, x)
V_y = diff(V, y)
# Differential
dV = V_x * dx + V_y * dy 
show(dV)
# Dérivée du premier ordre
sol=solve(dV==0, dy)
show(sol[0]/dx)
# Dérivée du second ordre
y_x=sol[0].rhs()/dx
show(y_x)
hh=y_x.function(x,y)
y=function('y')(x)
hh_x=diff(hh(x,y),x).full_simplify().subs(diff(y(x), x)==y_x).full_simplify() 
show(hh)
show(hh_x)

$\frac{\mathit{dy}}{\mathit{dx}} = -\frac{\frac{\partial}{\partial x}V\left(x, y\right)}{\frac{\partial}{\partial y}V\left(x, y\right)}$

$-\frac{\frac{\partial}{\partial x}V\left(x, y\right)}{\frac{\partial}{\partial y}V\left(x, y\right)}$

Now I will work on the substitution of the chosen function. And when I will have found I will come back.

edit flag offensive delete link more

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer

Question Tools

1 follower

Stats

Asked: 2020-04-24 11:41:04 -0600

Seen: 256 times

Last updated: Dec 03 '20