9 N[0] = r[0] * (r[0] + 1) * r[1] * (r[1] + 1) / 4;
10 N[1] = r[0] * (r[0] - 1) * r[1] * (r[1] + 1) / 4;
11 N[2] = r[0] * (r[0] - 1) * r[1] * (r[1] - 1) / 4;
12 N[3] = r[0] * (r[0] + 1) * r[1] * (r[1] - 1) / 4;
13 N[4] = r[1] * (r[1] + 1) * (1 - r[0] * r[0]) / 2;
14 N[5] = r[0] * (r[0] - 1) * (1 - r[1] * r[1]) / 2;
15 N[6] = r[1] * (r[1] - 1) * (1 - r[0] * r[0]) / 2;
16 N[7] = r[0] * (r[0] + 1) * (1 - r[1] * r[1]) / 2;
17 N[8] = (1 - r[0] * r[0]) * (1 - r[1] * r[1]);
23 dN[0] = (r[0] + 0.5) * r[1] * (r[1] + 1) / 2;
24 dN[1] = (r[0] - 0.5) * r[1] * (r[1] + 1) / 2;
25 dN[2] = (r[0] - 0.5) * r[1] * (r[1] - 1) / 2;
26 dN[3] = (r[0] + 0.5) * r[1] * (r[1] - 1) / 2;
27 dN[4] = -r[0] * r[1] * (1 + r[1]);
28 dN[5] = (1 - r[1] * r[1]) * (r[0] - 0.5);
29 dN[6] = r[0] * r[1] * (1 - r[1]);
30 dN[7] = (1 - r[1] * r[1]) * (r[0] + 0.5);
31 dN[8] = 2 * r[0] * (r[1] * r[1] - 1);
33 dN[10] = (r[1] + 0.5) * r[0] * (r[0] - 1) / 2;
34 dN[11] = (r[1] - 0.5) * r[0] * (r[0] - 1) / 2;
35 dN[12] = (r[1] - 0.5) * r[0] * (r[0] + 1) / 2;
36 dN[13] = (1 - r[0] * r[0]) * (r[1] + 0.5);
37 dN[14] = r[0] * r[1] * (1 - r[0]);
38 dN[15] = (1 - r[0] * r[0]) * (r[1] - 0.5);
39 dN[16] = -r[0] * r[1] * (1 + r[0]);
40 dN[17] = 2 * r[1] * (r[0] * r[0] - 1);
41 dN[9] = (r[1] + 0.5) * r[0] * (r[0] + 1) / 2;