(1.1).
. (2.1)
1) Δ > 0, (1.1) .
2) Δ = 0, (1.1) .
3) Δ < 0, (1.1) .
2.1 :
)
.
)
Δ < 0 .
, (1.1) () . :
, . (2.2)
φ(x,y) ψ(x,y) , (x,y) (ξ,η) , :
. (2.3)
(2.3) , (2.2) .
:
(2.4)
ϳ (2.4) (1.1)
(2.6)
:
(2.7)
ϳ (2.7) (2.6) :
. (2.8)
, (2.9)
(2.8) (1.1).
, φ(x,y) ψ(x,y) , , , .
2.1 г
φ(x,y) ψ(x,y , . , (2.7),
(2.10)
(2.10) . :
. (2.11)
(2.11) :
(2.12)
, (2.11) :
, (2.13)
, . (2.14)
(2.13) , :
(2.15)
. (2.16)
(2.15) (2.16) , . (2.15) (2.16) . (2.13), (2.10).
, (2.8). , (2.9).
. (2.17)
2.2
.
|
|
.
, .
:
1) ; ; , ;
2) ; ; , .
(2.4)
;
.
ϳ ,
,
.
, :
.
,
.
2.2 г
(1.1) , ,
. (2.18)
.
, , (1.1)
(2.19)
, , (2.20)
(2.15) (2.16) , ,
, . (2.21)
, .
, , (2.22)
(2.19), (1.1)
.
2.3
.
, .
:
1) ; ; , ;
2) ; , .
, (2.22)
, .
(2.4)
,
.
ϳ ,
,
.
2.3 г
(1.1) , , ,
. (2.23)
.
,
(2.24)
, (2.24) .
, (2.25)
.
(2.25), . , .
2.4 .
.
, .
(2.25)
, , .
г ,
, (2.7) .
(2.4)
;
;
.
ϳ ,
.
Maple
2.5
.
Maple.
|
|
> a[1]:= 4;a[2]:=4;a[3]:=1;a[4]:=0;a[5]:=-2;a[6]:=0;a[7]:=0;
> equ:=a[1]*diff(u(x,y),x,x)+a[2]*(x,y diff(u(x,y),x,y)+ +a[3]*diff(u(x,y),y,y)+a[4]*diff(u(x,y),x)+a[5]*diff(u),y)+ +a[6]*u(x,y)+a[7]=0;
equ:=
> eq:=lhs(equ);
equ:=
> A:= linalg[matrix](2,2,[coeff(eq,diff(u(x,y),x,x)), coeff(eq,diff(u(x,y),x,y))/2, coeff(eq,diff(u(x,y),x,y))/2, coeff(eq,diff(u(x,y),y,y))]);
> Delta:=simplify(linalg[det](A));
, .
.
> A[1,1]*z^2-2*A[1,2]*z+A[2,2]=0;res1:=solve(A[1,1]*z^2-2*A[1,2]*z+A[2,2],z);
> subs(y=(x),res1[1]);res2:=dsolve(diff(y(x),x)=%,y(x));
. .
> res2:=subs(y(x)=y,res2);
> itr:={xi=solve(res2,_C1),eta=y};
itr:=
> tr:=solve(itr,{x,y}); PDEtools[dchange](tr,eq,itr,[eta,xi],simplify)=0;
tr:=
:
> itr:={xi=solve(res2,_C1),eta=x};
itr:=
:
> tr:=solve(itr,{x,y});
PDEtools[dchange](tr,eq,itr,[eta,xi],simplify)=0;
tr:=
2.6
Maple.
> a[1]:= 3;a[2]:=2;a[3]:=-1;a[4]:=2;a[5]:=3;a[6]:=0;a[7]:=0;
>equ:=a[1]*diff(u(x,y),x,x)+a[2]*diff(u(x,y),x,y)+a[3]*diff(u(x,y),y,y)+a[4]*diff(u(x,y),x)+ +a[5]*diff(u(x,y),y)+a[6]*u(x,y)+a[7]=0;
equ:=
> eq:=lhs(equ);
eq:=
> A:= linalg[matrix](2,2,[coeff(eq,diff(u(x,y),x,x)), coeff(eq,diff(u(x,y),x,y))/2, coeff(eq, diff(u(x,y),x,y))/2, coeff(eq,diff(u(x,y),y,y))]);
> Delta:=simplify(linalg[det](A));
, .
.
>A[1,1]*z^2-2*A[1,2]*z+A[2,2]=0;res1:=solve(A[1,1]*z^2-2*A[1, 2]*z+A[2,2],z);
> res2:={seq(dsolve(diff(y(x),x)=res1[i],y(x)),i=1..2)};
> res2:=subs(y(x)=y,res2);
, . .
> {seq(solve(res2[i],_C1),i=1..nops(res2))};
> itr:={xi=solve(res2[1],_C1),eta=solve(res2[2],_C1)};
.
>tr:=solve(itr,{x,y});PDEtools[dchange](tr,eq,itr,[eta,xi], simplify)=0;
2.7
> a[1]:=3;a[2]:=2;a[3]:=1;a[4]:=2;a[5]:=3;a[6]:=0;a[7]:=0;
>equ:=a[1]*diff(u(x,y),x,x)+a[2]*diff(u(x,y),x,y)+a[3]*diff(u(x,y),y,y)+[4]*diff(u(x,y),x)+ +a[5]*diff(u(x,y),y)+a[6]*u(x,y)+a[7]=0;