# Implicit differentiation in Matlab 7.5.0 (R2007b) ?

Discussion in 'Programmer's Corner' started by farmosh203, Jan 17, 2008.

1. ### farmosh203 Thread Starter Member

Nov 26, 2006
20
0
I was trying to look up the command to help a friend with his homework for implicit differentiation. I couldn't find it in the help menu and the following code gave me:

>> clear
>> syms x y
>> H = y^2-x^3*(2-x);
>> idiff(H,x,y)
??? Undefined function or method 'idiff' for input arguments of type 'sym'.

Does anyone know the command to implicitly differentiate? Thanks.

2. ### Dave Retired Moderator

Nov 17, 2003
6,960
159
I haven't tried this myself: Couldn't you use the differentated function derived through the DIFF function, then multiply the function by $\frac{d}{dx_{i}}$, where $dx$$_{i}$ is the ith variable in a multivariable equation?

Actually have a look at http://www.math.fsu.edu/~sachutha/MAT3930/lab9_fall05.doc (Note this is a Word document, there is a HTML version here)

Dave

3. ### farmosh203 Thread Starter Member

Nov 26, 2006
20
0
Great, thanks for the link Dave.