area --> vector area

Former-commit-id: bcab63f31b0a47886fdc9870a153a3fe26bd9ea8

tutorial/500_Parametrization.md

@@ -89,7 +89,7 @@ which can be rewritten in matrix form as:
 
 \\[ E_{LSCM}(\mathbf{u},\mathbf{v}) = \frac{1}{2} [\mathbf{u},\mathbf{v}]^t (L_c - 2A) [\mathbf{u},\mathbf{v}] \\]
 
-where L_c is the cotangent laplacian matrix and A is a matrix such that \\( [\mathbf{u},\mathbf{v}]^t A  [\mathbf{u},\mathbf{v}] \\) is equal to the area of the mesh.
+where L_c is the cotangent laplacian matrix and A is a matrix such that \\( [\mathbf{u},\mathbf{v}]^t A  [\mathbf{u},\mathbf{v}] \\) is equal to the _vector area_ of the mesh.
 
 Using libigl, this matrix energy can be written using a few lines of codes. The cotangent matrix can be computed using igl::cotmatrix: