# Assumptions on symbolic functions

I have a symbolic function f = function('f')(x). Is there a way to assume it is real and get abs(exp(I*f)) = 1?

Assumptions on symbolic functions

add a comment

1

None at the moment, as far as I know.

Note however that :

`maxima`

has such a facility (see`maxima.declare?`

) ;- similarly,
`Sympy`

has such a facility (it even has two, the newer progressively replacing the older) ; - there are some reported bugs pointing the the way
`sage`

handles assumptions and tests thereof, and these bugs are worked on.

You might try to isolate the part of your computations where you need such a handling, do them in maxima or Sympy, and reimport the relevant results.

Note also that you can

```
assume(f(x)>0)
```

But that won't do a thing about `bool(f(2*x+1)>0)`

...

Asked: **
2018-03-16 07:39:00 -0600
**

Seen: **123 times**

Last updated: **Mar 17 '18**

desolve not using/understanding assume()

Is there any way to define an as-yet-unknown function?

Use the properties of inverse functions to find the exact value of the expression

Question about ordered pairs and dictionaries.

assume certain properties of the output of a function

assume() seems not to work for a specific case...

Generating functions and plotting them with different colors

How can I define a function with quaternion argument, and other non-vector input