... Put A 0 = A, A 1 = t1 (A 0), . . ., A m = tm (A m-1), and D (A) = A m,we have A 0 ⊆ A 1 ⊆ . . . ⊆ A m = D (A) ⊆ M. A problem A → B on a network (O,F) is called solvable if and only if ... Bi-1.4 Application ExampleNow we state an application example: solve a geometry problem. This example is solved by a program written in the programming language C++. The program gave us a good ... = A = {O1 .a , O1 .A} , A 1 = {O1 .a , O1 .A, O2 .A} , A 2 = { O1 .a , O1 .A, O2 .A, O1.b, O1.c }, A 3 = {O1 .a , O1 .A, O2 .A, O1.b, O1.c, O3 .a} , A 4 = {O1 .a , O1 .A, ...