.
. g , : F 1, F 2, , M F 1 M F 2 :
½ MF 1½ +½ MF 2½ = 2 a = const, (1)
.. M Îg, 2 a < 2 c =½ F 1 F 2½.
. F 1 F 2, Ox . Oy . F 1(c, 0), F 2( c, 0).
M (x, y) .
½ MF 1½ =, ½ MF 2½ =.
(1)
= 2 a .
:
x 2 2 xc + c 2 + y 2 = 4 a 2 4 a + x 2 + 2 xc + c 2 + y 2.
4 xc = 4 a 2 4 a Û a = a 2 + xc.
, :
a 2(x 2 + 2 xc + c 2 + y 2) = a 4 + 2 a 2 xc + x 2 c 2,
x 2(a 2 c 2) + a 2 y 2 = a 2(a 2 c 2).
a < c; b 2 = a 2 c 2, a 2 b 2,
+ = 1. (2)
, (2). : M (x, y) (2), (1).
(2) y 2 = b 2(1 ) ½ MF 1½, b 2 = a 2 c 2:
½ MF 1½ = = =
= =
= = =½ a ½.
, ½ MF 2½ =½ a + ½. (2) , ½ x ½ £ a ( 1), , a < c Þ .
½ MF 1½ +½ MF 2½ = a + a + = 2 a.
(2) .
.
1. (2) , ½ x ½ £ a, ½ y ½ £ b. , , .
, , . , , .
2. A 1(a, 0), A 2( a, 0), B 1(0, b), B 2(0, b), . A 1 A 2 B 1 B 2 , . a b .
3. , .
, M (x, y) .
(x, y) (2). (x, y), ( x, y), ( x, y), , M Ox, Oy O .
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4.
g¢: X 2 + Y 2 = a 2 (**)
Oy k = a/b. , M ¢(X, Y)Î g¢ M (x, y),
x = X, X = x ,
y = Y. Û Y = y.
(**), , M (2), .. M Î g.
5. s . , l = s I , l 1/cos a , a s . , , 4, .
6. , :
x = a cos a,
y = b sin a, t Î R .
.
. g , : F 1, F 2, , M F 1 M F 2 :
½ ½ MF 1½ ½ MF 2½½ = 2 a = const, (3)
.. M Îg, 2 a < 2 c =½ F 1 F 2½.
. F 1 F 2, Ox . Oy . F 1(c, 0), F 2( c, 0).
M (x, y) .
½ MF 1½ =,
½ MF 2½ =.
(3)
= 2 a +.
, .
x 2(c 2 a 2) a 2 y 2 = a 2(c 2 a 2).
. .
a < c; b 2 = c 2 a 2, a 2 b 2
= 1. (4)
, (4). : M (x, y) (4), (3). (4) y 2 = b 2( 1) ½ MF 1½, b 2 = c 2 a 2. ,
½ MF 1½ =½ a ½, ½ MF 2½ ==½ a + ½. (**)
. .
(4) , x 2 = a 2(1+ ) Þ ½ x ½ ³ a, c > a. , (**) x ³ a
½ MF 1½ = a, ½ MF 2½ = a +,
x £ a
½ MF 1½ = a , ½ MF 2½ = a .
(3).
(4) .
.
1. , M (x, y)
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x 2 = a 2(1+ ) Þ ½ x ½ ³ a,
(4) Þ
x 2 > Û ½ x ½>½ y ½.
, . .
2. Ox A 1(a, 0), A 2( a, 0), . Oy . a b .
3. , , , .
4. l 1: y = x l 2: y = x .
, .
, M (x, y) , M ¢(x, y ¢) . M , ½ MM ¢½.
½ MM ¢½ =½ y ¢½ ½ y ½.
(y ¢)2= x 2, y 2 = b 2( 1) (***)
, ½ x ½ ¾ ¥ ½ y ¢½ ¾ ¥ ½ y ½ ¥. ,
(y ¢)2 y 2 = b 2 Û ½ y ¢½ ½ y ½ = ¾ 0 ½ x ½ ¾ ¥.
, = 0. (4) 1 0. , ½ x ½ £ a, ½ y ½ £ b. . .
5. a = b .
x 2 y 2 = a 2 , (5)
l 1: y = x, l 2: y = x . , l 1 ^ l 2 , Ox ¢ y ¢, Oxy 45. :
x = (x ¢+ y ¢),
y = ( x ¢+ y ¢).
(5)
2 x ¢ y ¢= a 2 Û y ¢= ,
k = a 2/2. , .
6. :
x = a ch t, x = a (t + 1/ t),
y = b sh t, t Î R . y = b (t 1/ t), t Î R \{0}.
+ , .
. .
7.
g¢: = 1,
g, (4). , , , .