# How to satisfy the periodic boundary conditions of the first derivative and the second derivative at the same time

**URL:** https://community.freefem.org/t/how-to-satisfy-the-periodic-boundary-conditions-of-the-first-derivative-and-the-second-derivative-at-the-same-time/1807
**Category:** General Discussion
**Created:** [June 11, 2022, 12:57am UTC](https://community.freefem.org/t/how-to-satisfy-the-periodic-boundary-conditions-of-the-first-derivative-and-the-second-derivative-at-the-same-time/1807 "2022-06-11T00:57:31Z")
**Posts on this page:** 1
**Page:** 1

<div class="post-metadata">

### Author: ![Qianrui](https://avatars.discourse-cdn.com/v4/letter/q/9fc348/32.png) [@Qianrui](https://community.freefem.org/u/Qianrui)
#### Post date: [June 11, 2022, 12:57am UTC](https://community.freefem.org/t/how-to-satisfy-the-periodic-boundary-conditions-of-the-first-derivative-and-the-second-derivative-at-the-same-time/1807/1 "2022-06-11T00:57:31Z")

</div>

How to satisfy the periodic boundary conditions of the first derivative and the second derivative at the same time？

> fespace Uhf(Thf,P3,periodic=[[1],[2]]);

![屏幕截图 2022-06-09 181327](https://canada1.discourse-cdn.com/flex030/uploads/freefem/original/2X/2/2c12bf39ecf32fc3a71877e8fb6ae97266f0c754.png)