(9). O ¢ x ² y ², O ¢ x ¢ y ¢ a. :
x ¢ = x ²cos a y ²sin a,
y ¢ = x ²sin a + y ²cos a.
(9):
11(x ²cos a y ²sin a)2 + 2 12(x ²cos a y ²sin a)(x ²sin a + y ²cos a) +
+ 22(x ²sin a + y ²cos a)2 + ¢ = 0,
. x ² y ²
12sin2a + ( 22 11)sin acos a + 12cos2a
, cos2a:
12 tg2a + ( 11 22) tg a + 12 = 0. (15)
tg a,
D = ( 11 22)2 + 12 ³ 0.
, (14) , . a, , x ² y ².
l1(x ²)2 + l2(y ²)2 + = 0. (16)
, l1 l2
= 0;
:
l2 s l + d = 0, (17)
s = trace A = 11 22 A. .
l1+ l2 = s , l1l2 = d.
O ¢ x ² y ²
A¢ =, d¢= det A¢= l1l2 = d, s ¢= trace A¢ = l1+l 2 = s,
l1 0 0
D¢ =0 l2 0 = l1l2 (D/d) = D.
0 0 D/d
, d¢= d, s ¢= s, D¢ = D, .. d, s, D . .
1 : D ¹ 0. , (16)
+ = 1. (18)
a 2 = |D/l1d|, b 2 = |D/l2d|.
) d > 0, s D < 0. l1l2> 0, .. l1 l 2 , (l1+ l 2)D < 0, .. D l1 l 2. (17) , (15) :
+ = 1.
) d > 0, s D > 0. (18) ,
+ = 1.
, . .
) d < 0, D ¹ 0. l1 l 2 , (17) .
= 1 = 1.
.
2 : D = 0. (15) ( ):
l1 x 2 + l 2 y 2 = 0. (19)
a 2 =½l1½, b 2 =½l2½.
) d < 0. l1 l 2 (18)
a 2 x 2 b 2 y 2 = 0 Û
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Û (ax b y)(ax + b y) = 0.
, ax by = 0 ax + by = 0. , , O ¢ .
) d > 0. l1 l 2 (19)
a 2 x 2+ b 2 y 2 = 0 Û (ax i b y)(ax + i b y) = 0.
(i ). , . O ¢ .
d = D = 0 ( ), .
9. ( d = 0).
d = 0. , , (14). Ox ¢ y ¢.
x = x ¢ × cos a y ¢ × sin a,
y = x ¢ × sin a + y ¢ × cos a.
, (14), . , x ¢ y ¢:
l1 x ¢2 + l 2 y ¢2 + 2 b 1 ¢ + 2 b 2 ¢ + = 0, (20)
, , ,
b 1= a 1 × cos a + a 2 × sin a, b 2 = a 1 × sin a + a 2 × cos a.
l1 l 2 (17). d = l1l2 = 0, . l1.
l 2 y ¢2 + 2 b 1 ¢ + 2 b 2 ¢ + = 0. (21)
0 0 b 1
D = 0 l2 b 2 = l2 b 12.
b 1 b 2
1 : D = 0 Û b 1= 0. l 2 y ¢2 + 2 b 2 ¢ + = 0. :
l 2( y ¢ 2 + ¢ + ) + = 0 Û l 2( y ¢ + )2 + = 0.
¢= (b 12- l 2 ) /l 2, a 2 =½ ¢½ :
x ²= x ¢ ,
y ²= y ¢ + ,
O ¢(0, b 1/l2) Ox ¢ y ¢(, Ox ¢ y ¢).
(y ²)2 = a 2.
) ¢ > 0 Þ (y ²)2 = a 2, .. y ² = a y ² = a. .
) ¢ > 0 Þ (y ²)2 = a 2, .. y ² = i a y ² = i a. , .
) ¢ = 0 Þ (y ²)2 =0. , .
2 : D ¹ 0 Û b 1¹ 0. , , (21) y:
l 22 + 2 b 1 ¢ + = 0,
:
l 22+ 2 b 1 = 0.
c ¢ = :
x ²= ¢ c ¢,
y ²= y ¢ + ,
O ¢ Ox ¢ y ¢.
l 2(y ²)2 + 2 b 1 ² = 0 Û (y ²)2 = 2 p ²,
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p = 2 b 1/l 2. .
, , (8) (sign x x).
sign d | sign s D | - | |
+ | + = 1 | ||
+ | + | + = 1 | |
= 1 | |||
a 2 x 2 b 2 y 2 = 0 | |||
+ | a 2 x 2 + b 2 y 2 = 0 | ||
y 2 = 2 p, | |||
x 2 = a 2 x 2 = a 2 x 2 = 0 | ¥ |
.
1. , F (3, 3), Ox. .
. M (x, y) , MM ¢ , O. M Ox | MM ¢|=| y | (. ), | MF |=.
= 2| y |.
, , ; . , :
(x 3)2 +(y 3)2 = 4 y 2.
, :
(x 3)2 + y 2 6 y + 9 4 y 2= 0,
(x 3)2 3 y 2 6 y + 9 = 0,
(x 3)2 3(y 2 + 2 y + 1 4) = 0,
(x 3)2 3(y + 1)2 = 12.
x ¢= x 3,
y ¢= y + 1.
O ¢(3,1). 12:
= 1.
a =2 3,4, b =2. O ¢(3,1). 2).
2. . :
) 25 2 14 + 25 2 + 64 64 224 = 0.
. :
11 2 + 2 12 + 22 2 + 2 1 + 2 2 + = 0. (8)
d = ¹ 0,
¢( o, o), :
a 11 x o + a 12 y o + a 1 = 0, (10)
a 12 x o + a 22 y o + a 2 = 0.
', :
11 ' 2 + 2 12 ' ' + 22 ' 2 + ' = 0, (9)
' = 1 o+ 2 o+ . (12)
:
d = = 576 ¹ 0,
, . ( o, y o) (10):
25 o 7 o+ 32 = 0, Û 25 o 7 o = 32,
7 o+ 25 o 32= 0. 7 o+ 25 o= 32.
: x o=, o =, d x d , d y :
d x = = 32 = 32(18) = 576.
d y = = 32 = 3218 = 576.
x o= = 1, y o= = 1.
, ' (1, 1). ' ¢ ¢ ¢. :
x = x' + 1,
= ' 1.
; , : (9) ( , ), ' (12):
' = 32(1) 321 224 = 288.
:
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25 ¢2 14 ¢ ¢ + 25 ¢2 = 288. (9¢)
a, :
12tg2a + ( 11 22) tga 12 = 0, (15)
7tg2a +(25 25)tga + 7= 0,
tg2a = 1 tg a1= 1 tg a2 = 1.
. , , a, tg a > 0. : a =, sin a = cos a =.
' ''''. :
¢ = ²s a y ²sin a,
y ¢ = ²sin a + y ²cos a.
:
' = ('' y''),
y' = ('' + y'').
(9¢):
[25( ² y ²)2 14( ² y ²)( ²+ y ²) + 25( ² + y ²)2 ] = 288
[25 ²2 50 ² y ²+25 y ²2 14 ²+14 y ² + 25 ²2 + 50 ² y ²+ 25 y ²2] = 288.
, '' y'' . , .
[36 '' 2 + 64 y'' 2] = 288, 9 '' 2 + 16 y'' 2 = 144,
+ = 1.
= 4, b = 3. .
Oxy, ¢ ¢ x ¢ y ¢, Oxy '. a ¢ x ² y ². .
a = 45, . , , tg a = a / b, : 'x' b, 'y' . , , tg a = 3/4.
) 7 x 2+16 xy -23 y 2-14 x -16 y -218=0.
.
d= =-161-64=-225≠0.
, :
7 x o+ 8 y o-7=0, 7 x o+8 y o=7,
8 x o-23 y o-8=0, x o-23 y o=8.
:
d x = =-161-64=-225≠0, d y = =0.
x o= = -1, y o= =0.
O' (1, 0). ' O' ' '. :
x = x ¢ +1,
y = y ¢
c ¢ = -7 x o-8 y o+ c = -7-218 = -225. :
7 x ¢ 2 + 16 x ¢ y ¢ - 23 y ¢ 2 -225 = 0. (*)
a, (5):
8tg2a +30tga -8=0,
4tg2a +15tga -4=0,
D =225+64=289,
tga1= =, tga2= = -4.
: tga =. sina = , cosa =. (*) :
[7(4 x" - y")2+16(4 x" - y")(x" +4 y")-23(x" +4 y")2]=225,
[112 x" 2- 56 x"y" +7 y" 2+64 x" 2+ 240 x"y" -64 y" 2
-23 x" 2- 184 x"y " -368 y" 2]=225
, x"y" . , .
[153 x" 2-425 y" 2]=225,
9 x" 2-25 y" 2=225,
- =1.
a = 5, b = 3.
:
1) ¢(1, 0) - , ¢ x ¢|| x, ¢ y ¢|| y - ;
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2) , tg α = 1/4; ¢ " ¢ y" ( . 2)).
3) ¢ "y" : a = 5, b = 3;
4) , ;
5) : , .
) 9 x 2 - 24 xy + 16 y 2 - 20 x + 110 y - 50 = 0.
d = = 0
:
-12 tg2a-7tga+12 =0,
D =49+576=625,
tg a1 = =, tg a2 = = .
sina=; cosa= .
, (6) . :
[9(4 x ¢ - 3 y ¢)2 - 24(4 x ¢ - 3 y ¢)(3 x ¢ + 4 y ¢) + 16(3 x ¢ + 4 y ¢)2]
- (4 x ¢ - 3y¢) + (3 x ¢ + 4 y ¢) - 50 = 0,
[144 x ¢ 2 -216 x ¢ y' +81 y ¢ 2-288 x ¢2 -168 x ¢ y ¢ +288 y ¢ 2+ 144 x ¢2 +384 x ¢ y ¢ +296 y ¢ 2] -
16 x ¢ + 12 y ¢ + 66 x ¢ + 88 y ¢-50 = 0.
x ¢ y ¢ . , d = 0, :
25 y ¢ 2 + 50 x ¢ + 100 y ¢ -50 = 0, Û y ¢ 2 + 2 x ¢ + 4 y ¢ - 2 = 0. (*)
:
(y ¢2 + 4 y ¢ + 4) - 4 + 2 x ¢ - 2 = 0,
(y' + 2)2 + 2(x' 3) = 0.
:
O ¢(3,-2) ¢ x ¢ y ¢. , ¢ x ¢ y ¢.
y" 2=2 x" .
p = 1, ¢ x".
:
1. , tg α = 3/4 ;
2. ¢(3,2) x ¢ y ¢;
3. ¢ x" ¢ y".
4. ; , (*) y ¢= 0, x ¢ = 1. .. (1, 0) ¢ x ¢ y ¢ - ( x ¢ y ¢).