# Define another complicated function

**URL:** <https://community.freefem.org/t/define-another-complicated-function/1129>\
**Category:** General Discussion\
**Created:** [July 30, 2021, 9:56pm UTC](https://community.freefem.org/t/define-another-complicated-function/1129 "2021-07-30T21:56:51Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Aicha](https://avatars.discourse-cdn.com/v4/letter/a/ec9cab/32.png) [@Aicha](https://community.freefem.org/u/Aicha)\
**Post date:** [July 30, 2021, 9:56pm UTC](https://community.freefem.org/t/define-another-complicated-function/1129/1 "2021-07-30T21:56:51Z")

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Hi,  
real x1=0.0;  
real I1=I(x1,t)-0.5;  
where I is the solution of an system  
My question is: in FF++ how we define the function I1? Please.  
The difficulties is that FF++ don’t understant I(x1,t)

Thank you for the help

---

<div class="post-metadata">

**Author:** ![Aicha](https://avatars.discourse-cdn.com/v4/letter/a/ec9cab/32.png) [@Aicha](https://community.freefem.org/u/Aicha)\
**Post date:** [August 6, 2021, 3:26pm UTC](https://community.freefem.org/t/define-another-complicated-function/1129/2 "2021-08-06T15:26:05Z")

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Can any one help me please  
i try

```auto
func real I1(real x1,real t){return (I(x1,t)-0.5);}

```

but it’s not good

regards