-
..
2007 .
Ņ..3
1.
1.1. -5
1.2. ߅10
2.
2.1. ȅ...11
2.2. ......16
2.3. ۅ.....17
2.4. ۅ...18
Ņ...19
.20
:
Ź1 ( )
: y=f(x,y), y(a)=y0 - [a,b] h.
:
1. -.
2. .
3. .
. h.
Turbo Pascal 7.0, , . Turbo Pascal Borland , . Turbo Pascal 7.0 , , . , . , , (, - ..).
, , , , , . , . , , , .
1.
-
- : .
- :
1. : m+1,
xm,ym.
2. hp, .
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3. f (x,y), .
. . ( , ; , ; , .)
, xm,ym . ¢m=f(xm,ym), xm,ym. .1, , , L1 , .
, L1 , x=xm+1=xm+h.
L1 : y=ym+y¢m(x-xm) y¢=f(xm,ym) , xm+1=xm+h
ym+1=ym+h*f(xm,ym) 1.1.
x=xm+1 . , h, et=h2
, .1 , ym .
1.1 , . , - .
. : xm,ym xm+h,ym+hy¢m. , xm+1,ym+1. xm+1,ym+1 .2. xm+h,ym+hy¢m, L1. , L. , xm,ym L, L. , L , x=xm+1=xm+h, xm+1,ym+1.
L L
(xm,ym,h)=½[f(xm,ym)+f(xm+h,ym+y¢mh)] 1.2.
y¢m=f(xm,ym) 1.3.
L
y=ym+(x-xm)(xm,ym,h),
ym+1=ym+h(xm,ym,h). 1.4.
1.2, 1.3, 1.4 .
, , , f(x,y) :
f(x,y)=f(xm,ym)+(x-xm)f/x+(y-ym)f/x+¼ 1.5.
x=xm y=ym.
1.5 x=xm+h y=ym+hy¢m 1.3 y¢m,
f(xm+h,ym+hy¢m)=f+hfx+hffy+O(h2),
f xm,ym. 1.2 ,
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(xm,ym,h)=f+h/2(fx+ffy)+O(h2).
1.4
ym+1=ym+hf+h2/2(fx+ffy)+O(h3).
, h2, , , - .
. .3 , .2. , x=x+h/2. , y=ym+(h/2)y¢m.
(xm,ym,h)=f+(xm+h/2,ym+h/2*y¢m), 1.6.
y¢m=f(xm,ym) 1.7.
, , L*. , xm,ym L*, L0. x=xm+h xm+1,ym+1. y=ym+(x-xm)(xm,ym,h),
1.6.
ym+1=ym+h(xm,ym,h)1.8.
1.6, 1.7, 1.8 - . . ,
ym+1=ym+h(xm,ym,h) 1.9.
(xm,ym,h)=a1f(xm,ym)+a2f(xm+b1h,ym+b2hy¢m), 1.10.
y¢m=f(xm,ym) 1.11.
,
a1=a2=1/2;
b1=b2=1.