К.Ю. Богачёв - Практикум на ЭВМ. Методы приближения функций (1133845), страница 16
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!"# $B $Bx1. '&+-.- ')3 &)(-=37n XmXhf ginm = i(xy)2 67>>D I.13.2 :+6H4.7>hwij wkli(nmxy) = 0hwij wij i(nmxy) = nm4hwij wij i(nmxy) = nm2hw00 w00i(nmxy) = nm=1 j =1100f (xi yj )g(xi yj )::95 i 6= j 5 k 6= l:95 i 6= 0 5 j 6= 0:95 i 6= 0 j = 0 565 i = 0 j 6= 0-.7. C.25, wij +9-+=+/.67/ +-/+,5-76B/+ ,1.6;9/+=+ :9+520737/5; h i(xy) . +-7+97>7 1 :95C65?.FG.; @H/1<5; 5>77- 053 (4), =37 1+I@@5<57/-D ij 0D45,6;F-,; 0 (5). ,56H 053. >.-95< A 5 B 5>77>:xy)ij (f ) = hwij f i(nmhwij wij i(nmxy) hwij wiji(nmxy) : 5-+=7 :95C65?.FG.; @H/1<5; 5>77- 053(xy)nX;1 m;1Xhwij f inmw :Pf (x) =(xy) iji=0 j =0 hwij wij inmD45,67/57 1+I@@5<57/-+0 9.26+?7/5; +,HG7,-06;7-,; ,+=6.,/+ x 1.4 :95>7/7/57> .6=+95->. (I.13.11) :+ 1.?3+8 52 :797>7//DA x 5 y .ij =x 1.5.7.55$7; )! B>&C% #"C %#$%H,-B 1.?3D8 52 >7-+3+0 :95C65?7/5; :+ :797>7//D> x 5 y ;06;7-,; .::9+1,5>.<578 >/+=+467/.>5 7CDE70., :+,-9+7//+8 >7-+3+> /.5>7/BE5A 10.39.-+0 (,>.
x I.17). 95C65?.FG.; @H/1<5; (:+ 1.?3+8 52 :797>7//DA) 0D45,6;7-,; :+ @+9>H67 (I.17.2) , 1+I@@5<57/-.>5 (I.17.5).0737> 0,7 H4.,-0HFG57 0 :+,-./+017 2.3.45 65/78/+8 5/-79:+6;<55 -7/2+9/D>5 :9+520737/5;>5 +CO71-D. .25,/D7 @H/1<55: (9). "H/1<5+/.6D 2.3.F-,;0 (I.17.3):hi(x)i(u) = u Tbi(x) i = 0 1 : : : n ; 1hi(y)j (v) = v Tbj(y) j = 0 1 : : : m ; 1=37Zd f (y)g(y)f(x)g(x)(y)dx Sf g] = qdy:Sf g] = qc (d ; y )(y ; c)a (b ; x)(x ; a)(x)..Zb !"# $B $Bx1.
'&+-.- ')3 &)(-1016; I-+8 ,5,-7>D @H/1<5+/.6+0 >.-95<D A 0 (2) 5 B 0 (3) { 35.=+/.6B/D7(,>. 67>>H I.17.2): A = diag 2 : : : 2 2 Mn B = diag 2 : : : 2 2 Mm :.25, 0 :9+,-9./,-07 @H/1<58 { -7/2+9/DA :9+520737/58: (10). .25, 0 :9+,-9./,-07 @H/1<5+/.6+0 { -7/2+9/DA :9+520737/58:hi(xy)ij (f ) = i(j (f )) = Tbi(x)Tbj(y) f= Swij f ](xy)i = 0 1 : : : n ; 1 j = 0 1 : : : m ; 1=37Zb Zdf (x y)g(x y)dxdy:(b;x)(x;a)(d;y)(y;c)a c673+0.-76B/+, :95C65?.FG.; @H/1<5; Pf 2 Pn;1 (x) Pm;1 (y) H3+067-0+9;7,673HFG5> 65/78/D> H,6+05;> 5/-79:+6;<55:h b(x) b (y) i(xy) h b(x) b (y) i(xy)Pf Ti Tj= f Ti Tji = 0 1 : : : n ; 1 j = 0 1 : : : m ; 1(xy)Sf g]q1+-+9D7 ;06;F-,; >/+=+>79/D> ./.6+=+> H,6+058 (I.17.3).
,56H 3+1.2.//+=+ 0 x I.17 I-+ +2/.4.7-, 4-+ :95C65?.FG.; @H/1<5; Pf 2 Pn;1 (x) Pm;1 (y)97.652H7- >5/5>H>kf ; Pf k Sf ; Pf f ; Pf ] xy ! min0 :9+,-9./,-07 0,7A @H/1<58 Pf 2 Pn (x) Pm (y).(22 67>>D I.17.2 :+6H4.7>Swij wkl](xy) = 02Swij wij ](xy) = 42Swij wij ](xy) = 2Sw00 w00](xy) = 2 ;1);1:95 i 6= j 5 k 6= l:95 i 6= 0 5 j 6= 0:95 i 6= 0 j = 0 565 i = 0 j 6= 0-.7. C.25, wij +9-+=+/.67/ +-/+,5-76B/+ ,1.6;9/+=+ :9+520737/5; S ](xy) .+ -7+97>7 1 :95C65?.FG.; @H/1<5; 5>77- 053 (4), =37 1+I@@5<57/-D ij0D45,6;F-,; 0 (5). ,56H 053. >.-95< A 5 B 5>77>:(xy)Swij (f )ij f ]ij ==:Swij wij ](xy) Swij wij ](xy)..
!"# $B $Bx1. '&+-.- ')3 &)(-102 5-+=7 :95C65?.FG.; @H/1<5; 5>77- 053Pf (x) =nX;1 m;1XSwij f ](xy) w :(xy) iji=0 j =0 Swij wij ]D45,67/57 1+I@@5<57/-+0 9.26+?7/5; +,HG7,-06;7-,; ,+=6.,/+ x 1.4 :95>7/7/57> .6=+95->. (I.17.19) :+ 1.?3+8 52 :797>7//DA x 5 y .x 1.6.$5!;7 6$& 5$6%#; % ! -)! 55$7 ,6H4.7, 1+=3. 1.?3D8 52 >7-+3+0 5/-79:+6;<55 :+ :797>7//D> x 5 y;06;7-,; 1H,+4/+->/+=+467//D>, +:5,.//D8 0DE7 .6=+95-> 5/-79:+6;<55 -7/2+9/D>5 :9+520737/5;>5 >+?7- CD-B 2/.45-76B/+ H:9+G7/.H,-B f = f (x y) { @H/1<5; 30HA :797>7//DA, 2.3.//.; /. :9;>+H=+6B/517Sa b] Sc d]. H,-B -.1?7 2.3./D -+415 a = x1 < x2 < : : : < xn = b 5 c = y1 <y2 < : : : < ym = d , 5 1.?3D8 52 >7-+3+0 5/-79:+6;<55 :+ :797>7//D> x 5 y-.1+0, 4-+ 5/-79:+659HFG.; @H/1<5; /.
1.?3+> 52 +-9721+0 Sxi xi+1 ], Syj yj+1],-9+5-,; /72.05,5>+ (+- 39H=5A +-9721+0 Sxk xk+1], Syl yl+1], k 6= i , l 6= j ). +=3.>.-95<D A;1 5 B ;1 0 (5) CH3H- C6+4/+-35.=+/.6B/D>5, 5 52 -7+97>D 1 0D-71.7-,4-+ 5/-79:+659HFG.; @H/1<5; /. :9;>+H=+6B/517 Sxi xi+1 ] Syj yj+1] ,-9+5-,; /72.05,5>+ (+- 39H=5A :9;>+H=+6B/51+0 Sxk xk+1] Syl yl+1], k 6= i , l 6= j ).+I-+>H -7+97>H 1 >+?/+ :95>7/;-B /72.05,5>+ /.
1.?3+> 52 :9;>+H=+6B/51+0 Sxi xi+1] Syj yj+1]. J-+ +C,-+;-76B,-0+ :+20+6;7- -.1?7 9.,E595-B +C6.,-B:95>7/5>+,-5 .6=+95->.: @H/1<5; f >+?7- CD-B 2.3./. /7 -+6B1+ /. :9;>+H=+6B/517 Sa b] Sc d], . 5 /. 6FC+8 +C6.c-5,:973,-.05>+8 0 0537 +CO735/7/5;/7:79719D0.FG5A,; :9;>+H=+6B/51+0 S (Sxi xi+1 ] Syj yj+1]).ijx 1.6.1. -!; $5!;7;H,-B 1.?3D8 52 >7-+3+0 :95C65?7/5; :+ :797>7//D> x 5 y ;06;7-,;1H,+4/+-65/78/+8 5/-79:+6;<578 (,>.
x I.15). +=6.,/+ ,1.2.//+>H 0DE7 3+,-.-+4/+ 9.,,>+-97-B :95C65?7/57 /. :9;>+H=+6B/517 Sxi xi+1]Syj yj+1]. 95C65?.FG.; @H/1<5; (:+ 1.?3+8 52 :797>7//DA) 0D45,6;7-,; :+ @+9>H67 (I.15.1).0737> 0,7 H4.,-0HFG57 0 :+,-./+017 2.3.45 65/78/+8 5/-79:+6;<55 -7/2+9/D>5 :9+520737/5;>5 +CO71-D. .25,/D7 @H/1<55:ui 1(x) = xx ;; xxi+1 ui 2(x) = xx ;;xix x 2 Sxi xi+1 ]ii+1i+1iy;yy;yvj 1(y) = y ; yj+1 vj 2(y) = y ; jy y 2 Syj yj+1]:jj +1j +1j"H/1<5+/.6Di 1(u) = u(xi) i 2(u) = u(xi+1) j 1(v) = v(yj ) j 2(v) = v(yj+1):..
!"# $B $Bx1. '&+-.- ')3 &)(-103.-95<D A 0 (2) 5 B 0 (3) { 735/54/D7. .25, 0 :9+,-9./,-07 @H/1<58 { -7/2+9/DA :9+520737/58:wij kl(x y) = ui k(x)vj l (y) k l = 1 2:.25, 0 :9+,-9./,-07 @H/1<5+/.6+0 { -7/2+9/DA :9+520737/58:ij kl(f ) = i k (j l(f )) k l = 1 2-.7.ij 11(f ) = f (xi yj ) ij 12(f ) = f (xi yj+1)ij 21(f ) = f (xi+1 yj ) ij 22(f ) = f (xi+1 yj+1):+ -7+97>7 1 :95C65?.FG.; @H/1<5; 5>77- 053 (4):Pf =2 X2Xk=1 l=1ij klwij kl=37 1+I@@5<57/-D ij kl 0D45,6;F-,; 0 (5).
,56H A;1 = I , B ;1 = I 5>77>:ij kl = ij kl(f ): 5-+=7 :95C65?.FG.; @H/1<5; 5>77- 053Pf = f (xi yj ) xx ;; xxi+1 yy ;; yyj+1 +f (xi yj+1) xx ;; xxi+1 y y ;;yjyii+1 jj +1ii+1 j +1jx;xy;yx;xy;yij +1ij+f (xi+1 yj )xi+1 ; xi yj ; yj+1 +f (xi+1 yj+1) xi+1 ; xi yj+1 ; yj :+,-9+7//HF :95C65?.FGHF @H/1<5F 4.,-+ /.2D0.F- .
,6H4.7 1H,+4/+-65/78/+8 5/-79:+6;<55 -+- ?7 972H6B-.- >+?/+ :+6H45-B,:95>7/;; -7+97>H 1 /. 0,78 +C6.,-5 +:973767/5; @H/1<55 f .(x)5$#!. C+2/.45> 47972 S2 65/78/+7 :9+,-9./,-0+ /7:979D0/DA6+>./DA 65/58 /. +-97217 Sx1 xn] = Sa b] , 526+>.>5 x2 < x3 < : : : < xn;1 Y. 47972 S2(y) { 65/78/+7 :9+,-9./,-0+ /7:979D0/DA 6+>./DA 65/58 /. +-97217Sy1 ym] = Sc d] , 526+>.>5 y2 < y3 < : : : < ym;1 .0737> C.25,D :9+,-9./,-0.
S2(x) , S2(y) (,>. (I.16.2))Hi(x) 2 S2(x) Hi(x) (xk ) = ik i k = 1 2 : : : nHj(y) 2 S2(y) Hj(y) (yl ) = jl j l = 1 2 : : : m:,;1.; u 2 S2(x) 5 0,;1.; v 2 S2(y) 9.,16.3D0.7-,; :+ I-+>H C.25,H ,673HFG5>+C9.2+> (,>.( I.16.3)):u(x) =..nXk=1(x)u(xk )Hk (x) v(y) =mXl=1v(yl)Hl(y) (y): !"# $B $Bx1. '&+-.- ')3 &)(-104 1.47,-07 @H/1<5+/.6+0 0DC59.7> i(u) = u(xi), i = 1 2 : : : n , j (v) =v(yj ), j = 1 2 : : : m .
+=3. >.-95<D A 0 (2) 5 B 0 (3) { 735/54/D7Y C.25,0 :9+,-9./,-07 @H/1<58 { -7/2+9/DA :9+520737/58: wij (x y) = Hi(x) (x)Hj(y) (y),i = 1 2 : : : n , j = 1 2 : : : m Y C.25, 0 :9+,-9./,-07 @H/1<5+/.6+0 { -7/2+9/DA:9+520737/58: ij (f ) = f (xi yj ), i = 1 2 : : : n , j = 1 2 : : : m . + -7+97>7 1:95C65?.FG.; @H/1<5; 5>77- 053 (4), =37 1+I@@5<57/-D ij 0D45,6;F-,;0 (5). ,56H A;1 = I , B ;1 = I 5>77>: ij = ij (f ). 5-+=7 :95C65?.FG.;@H/1<5; 5>77- 053n XmXPf =f (xi yj )Hi(x)(x)Hj(y) (y):i=1 j =1x 1.6.2. -!; 55$7; # "C%#$%H,-B 1.?3D8 52 >7-+3+0 :95C65?7/5; :+ :797>7//D> x 5 y ;06;7-,;1H,+4/+-65/78/+8 .::9+1,5>.<578, :+,-9+7//+8 >7-+3+> /.5>7/BE5A 10.39.-+0 (,>.
x I.16). I-+> ,6H4.7 H3+C/77 :95>7/;-B -7+97>H 1 /. 0,78 +C6.,-5+:973767/5; @H/1<55 f .0737> 0,7 H4.,-0HFG57 0 :+,-./+017 2.3.45 65/78/+8 5/-79:+6;<55 -7/2+9/D>5 :9+520737/5;>5 +CO71-D. .25,/D7 @H/1<55 (,>. +:973767/5; 0 :973D3HG7> 9.23767):ui(x) Hi(x)(x) i = 1 2 : : : n vj (y) Hj(y)(y) j = 1 2 : : : m:"H/1<5+/.6Di(u) = u Hi(x) L2 (a b]) i = 1 2 : : : nj (v) = v Hj(y) L2(c d]) j = 1 2 : : : m:.-95<D A 0 (2) 5 B 0 (3) { -97A35.=+/.6B/D7, ,>. (I.16.8). .25, 0 :9+,-9./,-07@H/1<58 { -7/2+9/DA :9+520737/58:wij (x y) = Hi(x)(x)Hj(y) (y) i = 1 2 : : : n j = 1 2 : : : m:.25, 0 :9+,-9./,-07 @H/1<5+/.6+0 { -7/2+9/DA :9+520737/58:ij (f ) = i(j (f )) = f Hi(x)Hj(y) L2 (a b]c d]) i = 1 2 : : : n j = 1 2 : : : m:673+0.-76B/+, :95C65?.FG.; @H/1<5; Pf L2 f 2 S2(x) S2(y) H3+067-0+9;7,673HFG5> 65/78/D> H,6+05;> 5/-79:+6;<55:L2 f Hi(x)Hj(y) L2(a b]) = f Hi(x)Hj(y) L2 (a b]) i = 0 1 : : : n ; 1 j = 0 1 : : : m ; 1..
!"# $B $Bx1. '&+-.- ')3 &)(-1051+-+9D7 ;06;F-,; >/+=+>79/D> ./.6+=+> H,6+058 (I.16.6). ,56H 3+1.2.//+=+ 0 x I.16 I-+ +2/.4.7-, 4-+ :95C65?.FG.; @H/1<5; Pf = L2 f 2 S2(x) S2(y)97.652H7- >5/5>H>kf ; L2f kL2(a b]c d]) ! min0 :9+,-9./,-07 0,7A @H/1<58 L2 f 2 S2(x) S2(y) .+ -7+97>7 1 :95C65?.FG.; @H/1<5; 5>77- 053 (4), =37 1+I@@5<57/-D ij0D45,6;F-,; 0 (5).
95 I-+> :95>7/;7-,; .6=+95-> 52 x 1.4, . 36; H,1+97/5;0D45,67/58 36; >.-95< A 5 B ,-9+;-,; 5A LU -9.26+?7/5;.x 1.6.3. - >; $5!;7;H,-B 1.?3D8 52 >7-+3+0 :95C65?7/5; :+ :797>7//D> x 5 y ;06;7-,; 1H,+4/+-1HC547,1+8 5/-79:+6;<578 (,>. x I.19). +=6.,/+ ,1.2.//+>H 0DE73+,-.-+4/+ 9.,,>+-97-B :95C65?7/57 /. :9;>+H=+6B/517 Sxi xi+1] Syj yj+1].95C65?.FG.; @H/1<5; (:+ 1.?3+8 52 :797>7//DA) 0D45,6;7-,; :+ @+9>H67 (I.19.2), =37 1+I@@5<57/-D 2.3.F-,; (I.19.3).0737> 0,7 H4.,-0HFG57 0 :+,-./+017 2.3.45 65/78/+8 5/-79:+6;<55 -7/2+9/D>5 :9+520737/5;>5 +CO71-D.