How to assume a symbolic function as real

Hi everyone, I am new to symbolic math toolbox in Matlab, and I need help to do the following.

I need to declare a symbolic function of time a(t) - say it's an angle of a rotating vector - and I want to get rid of all the conj(a(t)) expressions when differentiating trigonometric functions of a(t).

I tried:

syms t a(t) real;
conj(a(t))

ans =

conj(a(t))

What's the correct way to do this?

Thanks in advance.

Answer 1

[Star Strider]

Use the assume function:

syms t a(t) real
assume(a(t),'real')
conj(a(t))

produces:

ans =

a(t)

[Sean de Wolski]

Beat me to it by 30s!

[Star Strider]

I’ve been there myself more often than I care to mention!

Thanks!

Answer 2

[Francesco]

Thank you for the answer, I'm trying this in Matlab 2012, and it still gives:

syms t a(t) real
assume(a(t),'real')
conj(a(t))

ans =

conj(a(t))

Has it something to do with the version I'm using, or am I doing something wrong?

Thanks

[Sean de Wolski]

That's quite possibly an improvement that's been incorporated since then. If your company/university is current on maintenance, you can upgrade at no additional cost.