how to define a variable as a function of another variable in symbolic toolbox

Hi I am just wondering whether is it possible to do following: define a variable as a function of x

    u=f(x)
Then,

    d/dx (u*x) = u'x + xu'

u' is first derivative of u w.r.t. x.

Is this possible to do using matlab symbolic toolbox?

[Azzi Abdelmalek]

It's not u'x + xu' but

u'x + x'u

[Star Strider]

You need to set it up correctly:

syms f(x) u(x)
ddx = diff(u*f,x)

—>

ddx(x) =

D(f)(x)*u(x) + f(x)*D(u)(x)

Answer 1

[Azzi Abdelmalek]

syms x u 
u=cos(x)
y=u*x
out=diff(y,x)

[Amit Kumar]

Thanks for your reply. But I do not want a specific function for u. I just want to define it as a generic function of x.

[Star Strider]

You need to set it up correctly:

syms f(x) u(x)
ddx = diff(u*f,x)

—>

ddx(x) =

D(f)(x)*u(x) + f(x)*D(u)(x)

[Amit Kumar]

Thanks!