MATLAB: Problem, when trying to differentate sin(f(x)), with variable x

diff differentation derivative sin cos

Hello!

I would like to try some basic functions in Matlab. I faced two problems, which seems unable to solve for me.

If I type:

a=sin(3*x)
b=diff(a,x)

Then I run it:

a=sin(3*x)(3*x)
b=3*D(sin(3*x))(3*x)

I think it should be:

a=sin(3*x)
b=3*cos(3*x)

Please tell me what is wrong with my little code! Thank you!

syms x
a=sin(3*x)
b=diff(a,x)

The result is

 b =
3*cos(3*x)

Hi, the file is not attached but if your answer correlates with this answer then there is nothing wrong with your code:

syms x
q = partfrac((x+1)/(4*x.^2-1))
int(q)

Have a look at the help and documentation for jacobian.

HTH