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Applied Mathematics, Calculus, and Differential Equations  233


                          Divergencł
                          Let G(x,y,z) be a vector function of scalar variableð x, y, and z
                          as defined above. The divergence of G(x,y,z), written div G,Łs
                          defined as the dot product of the del operator and G(x,y,z), as
                          follows:

                                          div G     • G(x,y,z)    G (x,y,z)/ x
                                                                        1
                                                G (x,y,z)/ y    G (x,y,z)/ z
                                                                     3
                                                   2

                          Curl
                          Let G(x,y,z) be a vector function of scalar variableð x, y, and z
                          as defined above. The curl of G(x,y,z), written curl G, is defined
                          as the cross product of the del operator and G(x,y,z), as follows:

                                       curl G   ( G (x,y,z)/ y    G (x,y,z)/ x)i
                                                                         2
                                                      3
                                             ( G (x,y,z)/ z    G (x,y,z)/ x)j
                                                  1
                                                                     3
                                             ( G (x,y,z)/ x    G (x,y,z)/ y)k
                                                                    1
                                                  2

                          Laplacian
                          Let G(x,y,z) be a vector function of scalar variableð x, y, and z
                          as defined above. The Laplacian of G(x,y,z), written Laplacian
                          G, is defined as follows:

                                                             2
                                                    2
                                                                         2
                                                                                2
                                                                   2
                                                                                      2
                                Laplacian G     G     G/ x     G/ y     G/ z                2
                          For a scalar function F(x,y,z), the Laplacian is defined as fol-
                          lows:
                                                                                     2
                                                                               2
                                                                         2
                                                     2
                                                             2
                                                                   2
                                 Laplacian F     F     F/ x     F/ y     F/ z              2
                          GradienŁ
                          Let F(x,y,z) be a scalar function of scalar variableð x, y, and z
                          as defined above. The gradient of F(x,y,z), written grad F,Łs
                          defined as follows:

                                   grad F     F   ( F/ x)i   ( F/ y)j   ( F/ z)k
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