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Degree 2 Fortin–Soulie on a triangle

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In this example:
• $$R$$ is the reference triangle. The following numbering of the subentities of the reference is used:
• $$\mathcal{V}$$ is spanned by: $$1$$, $$x$$, $$x^{2}$$, $$y$$, $$x y$$, $$y^{2}$$
• $$\mathcal{L}=\{l_0,...,l_{5}\}$$
• Functionals and basis functions:
$$\displaystyle l_{0}:v\mapsto v(\tfrac{2}{3},\tfrac{1}{3})$$

$$\displaystyle \phi_{0} = \frac{9 x^{2}}{2} - \frac{3 x}{2} - \frac{27 y^{2}}{16} + \frac{27 y}{16} - \frac{3}{8}$$

This DOF is associated with edge 0 of the reference element.
$$\displaystyle l_{1}:v\mapsto v(\tfrac{1}{3},\tfrac{2}{3})$$

$$\displaystyle \phi_{1} = 9 x y - 3 x + \frac{27 y^{2}}{4} - \frac{27 y}{4} + \frac{3}{2}$$

This DOF is associated with edge 0 of the reference element.
$$\displaystyle l_{2}:v\mapsto v(0,\tfrac{1}{3})$$

$$\displaystyle \phi_{2} = \frac{9 x^{2}}{2} + 9 x y - \frac{15 x}{2} + \frac{45 y^{2}}{16} - \frac{93 y}{16} + \frac{21}{8}$$

This DOF is associated with edge 1 of the reference element.
$$\displaystyle l_{3}:v\mapsto v(0,\tfrac{2}{3})$$

$$\displaystyle \phi_{3} = - 9 x y + 3 x - \frac{9 y^{2}}{4} + \frac{21 y}{4} - \frac{3}{2}$$

This DOF is associated with edge 1 of the reference element.
$$\displaystyle l_{4}:v\mapsto v(\tfrac{1}{2},0)$$

$$\displaystyle \phi_{4} = \frac{9 y^{2}}{2} - \frac{9 y}{2} + 1$$

This DOF is associated with edge 2 of the reference element.
$$\displaystyle l_{5}:v\mapsto v(\tfrac{1}{3},\tfrac{1}{3})$$

$$\displaystyle \phi_{5} = - 9 x^{2} - 9 x y + 9 x - \frac{81 y^{2}}{8} + \frac{81 y}{8} - \frac{9}{4}$$

This DOF is associated with face 0 of the reference element.