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(C1) 'DIFF(F,X,2)=SIN(X)+'DIFF(G,X); (C2) 'DIFF(F,X)+X^2-F=2*'DIFF(G,X,2); is NOT the proper format. The correct way is: (C3) 'DIFF(F(X),X,2)=SIN(X)+'DIFF(G(X),X); (C4) 'DIFF(F(X),X)+X^2-F(X)=2*'DIFF(G(X),X,2); The call is then DESOLVE([D3,D4],[F(X),G(X)]); If initial conditions at 0 are known, they should be supplied before calling DESOLVE by using ATVALUE. (C11) 'DIFF(F(X),X)='DIFF(G(X),X)+SIN(X); d d (D11) -- F(X) = -- G(X) + SIN(X) dX dX (C12) 'DIFF(G(X),X,2)='DIFF(F(X),X)-COS(X); 2 d d (D12) -- G(X) = -- F(X) - COS(X) 2 dX dX (C13) ATVALUE('DIFF(G(X),X),X=0,A); (D13) A (C14) ATVALUE(F(X),X=0,1); (D14) 1 (C15) DESOLVE([D11,D12],[F(X),G(X)]); X X (D16) [F(X)=A %E - A+1, G(X) = COS(X) + A %E - A + G(0) - 1] /* VERIFICATION */ (C17) [D11,D12],D16,DIFF; X X X X (D17) [A %E = A %E , A %E - COS(X) = A %E - COS(X)]
If DESOLVE cannot obtain a solution, it returns "FALSE".
(C3) IC1(D2,X=%PI,Y=0); COS(X) + 1 (D3) Y = - ---------- 3 X (C4) 'DIFF(Y,X,2) + Y*'DIFF(Y,X)^3 = 0; 2 d Y dY 3 (D4) -- + Y (--) = 0 2 dX dX (C5) ODE2(%,Y,X); 3 Y - 6 %K1 Y - 6 X (D7) ------------------ = %K2 3 (C8) RATSIMP(IC2(D7,X=0,Y=0,'DIFF(Y,X)=2)); 3 2 Y - 3 Y + 6 X (D9) - ---------------- = 0 3 (C10) BC2(D7,X=0,Y=1,X=1,Y=3); 3 Y - 10 Y - 6 X (D11) --------------- = - 3 3
a pot-pourri of Ordinary Differential solvers combined in such a way as to attempt more and more difficult methods as each fails. For example, the first attempt is with ODE2, so therefore, a user using ODE can assume he has all the capabilities of ODE2 at the very beginning and if he has been using ODE2 in programs they will still run if he substitutes ODE (the returned values, and calling sequence are identical). In addition, ODE has a number of user features which can assist an experienced ODE solver if the basic system cannot handle the equation. The equation is of the same form as required for ODE2 (which see) and the y and x are dependent and independent variables, as with ODE2. For more details, do PRINTFILE(ODE,USAGE,SHARE); .
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