7 
The corresponding normal equations become 
/ 4a 2 \ r 
4 dx 0 + |4cH \d(p + [dx\ = 0 
/ 4a 2 \ 
4dz 0 4- 14c H 1 dw + [dz] = 0 
8a 2 a 
-rdc-\—N 41 =0 
c c 
.2 
8a dx + aN 42 = 0 
4a' 
8a 4 
4c 4 I dx 0 4~ 14c 4—2 + 8a 1 dcp + c[dx] 4—N 43 = 0 
4a ; 
4c 4 J ¿/zq 4-14c 2 4—2—b 8a~^ dco 4- c[dz] 4~ —~N 44 = 0 
The symbols used have the following definitions 
[dx] = dxi 4- dx 2 4- dx 3 4- dx 4 
[dz] = dzi 4- dz 2 4- c/z 3 4- dz 4 
(7) 
N 41 = — dx l — dx 2 4- dx 3 4- dx 4 — dz x 4- dz 2 +dz 3 — dz 4 
N 42 = dx 3 — dx 2 —dx 3 4- dx 4 + dz l + dz 2 —dz 3 —dz 4 
N43 = dxi 4- dx 2 4- dx 3 4- dx 4 4- dz 3 — dz 2 4- dz 3 — dz 4 
N 44 = dz3 + dz 2 + dz 3 +dz 4 + dx\ — dx 2 4* dx 3 — dx 4 
The solutions of the normal equations are 
[dx] a 2 4-c 2 
dx 0 =- 
dzr>= — 
4 4 a 2 
[dz] a 2 4-c 2 
( — dz t + dz 2 — dz 3 4- dz 4 ) 
4 a' 
( — dx t 4- dx 2 — dx 3 4- dx 4 ) 
(8) 
(9) 
dc= N 4 , 
8 a 
dx= 
N42 
8 a 
(10) 
(11) 
t 
dm— —A — dz i +dz 2 — dz 3 + dz 4 ) 
4 a 
(12)