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triangle - Triangle reference element

 triangle(7rheolef) rheolef-6.7 triangle(7rheolef)

NAME

triangle - Triangle reference element

DESCRIPTION

The triangle reference element is

```        K = { 0 < x < 1 and 0 < y < 1-x }

```

NUMBERING

```      y
```
```      2
| +
|   +
|     +
|       +
0---------1   x

```
Curved high order Pk triangles (k >= 1), in 2d or 3d geometries, are supported. These triangles have additional edge-nodes and face-nodes.

THESE NODES ARE NUMBERED AS

first vertex, then edge-node, following the edge numbering order and orientation, and finally the face internal nodes, following the triangle lattice. See below for edge numbering and orientation.

```      2               2               2
| +             | +             | +
|   +           7   6           9   8
5     4         |     +        10 14  7
|       +       8   9   5      11 12 13 6
|         +     |         +     |         +
0-----3-----1   0---3---4---1   0--3--4--5--1
P2              P3              P4

```

IMPLEMENTATION

```const size_t dimension = 2;
const Float  measure = 0.5;
const size_t n_vertex = 3;
const point vertex [n_vertex] = {
point(0, 0),
point(1, 0),
point(0, 1) };
const size_t  n_edge = 3;
const size_t edge [n_edge][2] = {
{ 0, 1 },
{ 1, 2 },
{ 2, 0 } };

```
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