Simplifying symbolic expression to get real of real function in it.

I m having a complicated symbolic expression which consists of real function with a complex symbolic expression as an argument to it. I want to simplify this complicated symbolic expression so that i get an expression which does not have real function in it.

How do i do it?

[Torsten]

Please give an example - or even better: post your code.

Answer 1

[Walter Roberson]

syms x
(x^3 + x)/x^2 + 5

ans = 

real(ans)

ans = 

You can see that if you have a real() call then the Symbolic Toolbox already automatically picks out the portions that are certain to be real and moves them outside the real() call.

If you have a real() call that is not simplifying the expression, then either the expression contains calls to unknown functions

syms F(x)
real(F(x) + 5)

ans = 

or else the expression is in complex variables.

When you syms a variable, by default the variable is assumed to be complex, unless you add the real flag to the syms call

syms x real

or else you use assume or assumeAlso to explicitly mark the variable as real, or to add an assertion that implies the variable is real

syms y
assume(y > 0)
real(y + 5)

ans = 

Here, the assumption of >0 can only be satisfied if y is real, so you get y is real "for free"