public Jacobian(Element element, UniversalElement universalElement)
{
double[,] tab = new double[2, 2];
for (int i = 0; i < element.GetNodes().Length; i++)
{
tab[0, 0] += universalElement.GetdKsi(i) * element.GetNode(i).GetX();
tab[0, 1] += universalElement.GetdKsi(i) * element.GetNode(i).GetY();
tab[1, 0] += universalElement.GetdEta(i) * element.GetNode(i).GetX();
tab[1, 1] += universalElement.GetdEta(i) * element.GetNode(i).GetY();
}
det = MatrixOperations.determinant(tab);
inverseJacobian = MatrixOperations.inverse(tab);
dNdx = new double[4];
dNdy = new double[4];
for (int i = 0; i < 4; i++)
{
dNdx[i] = GetInverseJacobian()[0, 0] * universalElement.GetdKsi(i) - GetInverseJacobian()[0, 1] * universalElement.GetdEta(i);
dNdy[i] = -GetInverseJacobian()[1, 0] * universalElement.GetdKsi(i) + GetInverseJacobian()[1, 1] * universalElement.GetdEta(i);
}
}
