xD =, yD =.
xB = 2 xD xC = 1, yB = 2 yD yC =1, B (1, 1).
, , , (-2,-7). : Δ ABC .
:
x =, yD =,
l1:l2, .. ½ AC ½:½ BC ½=l1:l2.
, 2:1, . 2:1.
xP = = = ,
yP = = = .
: (2,7), B (1, 1), P.
3. A ( 4,2), B (9, 7), C (2, 4) ABC. AD D.
. , =.
(13, 9), (6,2);
½½= = 5, ½½= = 2.
BD: DC = 5 : 2. , (. 16)
xD = = = 4,
yD = = = , D (4, ).
, A D. . , , . , =, (7, 1).
AD: = y + 2 Û x 7 y 10 = 0.
: D (4, ), AD: x 7 y 10 = 0.
4. x y 3 = 0, 5 x + 4 y 9 = 0 ABC A ( 1, 2). .
. , A . M. , M. :
l( x y 3) + m(5 x + 4 y 9) = 0.
l m ; , m = 1 ( m = 0 , ). :
(l + 5) x + (l + 4) y 3l 9 = 0.
, A ( 1, 2). :
(l + 5) + 2(l + 4) 3l 9 = 0,
6l 6 = 0, l = 1.
l :
4 x + 5 y 6 = 0.
: 4 x + 5 y 6 = 0.
5. SABC: A (3, 7, 1), B (1, 9, 2), C (3, 6, 6) S (6,5,2). ABC SD. D S ¢, S .
. p = ABC:
= (2, 1, 1), = (0,1, 5).
, A (x o, y o, z o) (a 1, a 2, a 3), (b 1, b 2, b 3)
x x o y y o z z o
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a 1 a 2 a 3 = 0.
b 1 b 2 b 3
:
x + 3 y 7 z 1
2 2 1 = 0.
0 1 5
:
, (11,10,2) . h = SD. , A (x o, y o, z o) (a 1, a 2, a 3)
x = x o + a 1 t ,
y = y o + a 2 t ,
z = z o + a 3 t .
:
x = 6 + 11 t ,
h: y = 5 10 t , (*)
z = 2 2 t .
. p. p. l π:
11(6 + 11 t) 10(5 10 t) 2(2 2 t) + 105 = 0,
66 + 121 t + 50 + 100 t + 4 + 4 t + 105 = 0,
225 y = 225, t = 1.
t l D (5, 5, 0).
: . , S, . SS ¢ SD . tD = 1 S D, S S ¢ t ¢= 2 tD = 2. (*), S ¢(16, 15; 2).
: ABC: 11 x 10 y 2 z +105 = 0, D (5, 5, 0), S ¢(16, 15; 2),
x = 6 + 11 t ,
SD: y = 5 10 t ,
z = 2 2 t .
6. l p :
, l p l ¢ l . l p.
. : (1,1, 2) : A (6, 0, 2), :
(5,2, 4). , l ½½ p , ^ .. = 0. :
= 51 2(1) + 42 = 15 ¹ 0.
, l π. l p :
sin a =;
|| = =, || = = = 3.
sin a = =.
A o A , B = l I π. l ¢= A o B . B. l :
x = 6 + t,
l: y = t,
z = 2 + 2 t,
π. l π:
5(6 + t ) 2( t ) + 4(2 + 2 t ) + 7 = 0,
30 + 5 t + 2 t + 8 + 8 t + 7 = 0,
15 t = 45, t = 3.
t l B (3, 3, 4). h = AA o. h . h
x = 6 + 5 t,
h: y = 2 t,
z = 2 + 4 t,
π, A o:
5(6 + 5 t ) 2(2 t ) + 4(2 + 4 t ) + 7 = 0,
30 + 25 t + 4 t + 8 + 16 t + 7 = 0,
45 t = 45, t = 1.
t h A o(1, 2,2). l': A o B (2, 1,2) :
.
7. l
2 x +2 y z 1=0,
4 x 8 y + z 5= 0,
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A (5,6,1). , l.
. P , A l. P. p, A p1 p2. : (2, 2,1), (4,8, 1). p . :
x + 5 y 6 z 1
2 2 1 = 0.
4 8 1
6( x + 5) 6( y 6) 24( z 1) = 0 .
6:
x + 5 + y 6 + 4( z 1) = 0,
x+ y+ 4 z 5 = 0.
P p, p1 p2 . , , :
x + y + 4 z 5 = 0,
4 x 8 y + z 5 = 0,
2 x + 2 y z 1 = 0.
, P (1,0,1). , , P AB B (7,6,1).
P , A l . . , . 10. . 8.
8. D ABC A (9, 5, 1), B (3, 8, 4), C (9,13,8) AD. D, AD, h =½ AD ½ h, SD ABC .
. , D : D = π I BC, π , A BC. . (12,21,12). 3. p = , (4,7, 4). π, A o(x o, y o, z o) (a, b, c), :
a (x x o) + b (y y o) + c (z z o) = 0.
:
4(x 9) - 7(y 5) - 4(z 1) = 0,
4 x - 7 y - 4 z + 3 = 0,
BC. :
x = 3 + 4 t,
BC: y = 8 7 t, (*)
z = 4 4 t,
D = π I BC, D π BC. BC π:
4(3 + 4 t ) 7(8 7 t ) 4(4 4 t ) + 3 = 0,
12 + 16 t 56 + 49 t 16 + 16 t + 3 = 0,
81 t = 81, t = 1.
t BC D (1, 1, 0). , A D, AD :
h = = 9.
, SΔ ABC = |´ |; ´, .
i j k i j k
´ = 12 3 3 = 27 4 1 1 = 27( i + 4 j 8 k) .
0 18 9 0 2 1
( : ).
SΔ ABC = 27 =.
SΔ ABC = | | h. h =.
| |= = 3 = 27.
h = 9. .
D , A BC, . M (t) BC; (*):
M (3 + 4 t, 8 7 t, 4 4 t).
A M (t):
h 2(t) = (9 + 3 4 t)2 + (5 8 + 7 t)2 + (1 4 + 4 t)2
= (12 4 t)2 + (3 + 7 t)2 + (3 + 4 t)2 =
= 144 96 t + 16 t 2 + 9 42 t + 49 t 2 + 9 24 t + 16 t 2 =
= 81 t 2 162 t + 162.
h 2(t) :
h 2(t) = 162 t 162; h 2(t) = 0 Þ t = 1.
t BC , D (1, 1, 0) A BC.
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9. (, , ). , , .
). p1: 2 y + z + 5 = 0, p2: 5 x + 4 y 2z +11 = 0.
. p1 p2
a 1 x + b 1 y + c 1z + d 1= 0, a 2 x + b 2 y + c 2z + d 2= 0,
p1½½ p2 Û = = ¹,
p1 = p2 Û = = =.
¹ ¹, . , .
cos a =,
.
(0, 2, 1), (5, 4,2), = 05 + 2 4 + 1(2);
|| = =, || = = 3.
, cos a = =.
: a = arccos.
) p1: x y + 2z + 8 = 0,
p2: 2 x y + 4z 12 = 0.
. :
, p1½½ p2 p1 ¹ p2. A (x, y, z) ,
h =.
Îp1. , p1. , : A o(0, 8, 0). A o p2 p1 p2 :
h = =.
10. p,
p1: 2 x y + 2= 0, p2: 5 x + 4 y 2 z 14 = 0,
(0, 3,2). l = p 1I p 2 ;
. p, , h 1 h 2 p1 p2 .
:
=
. 2 , .. p1 p2 . , , . p 1 , . , p1 + p2 . , +:
=,
3(-2 x + y - 2) = 5 x + 4 y 2 z 14,
p:11 x + y - 2 z - 14 = 0.
, l, .
p1 p2 : (2,1, 0), (5, 4,2). l . ( , = ´ , ^ ^ ):
i j k
= ´ = 2 1 0 = 2 i + 4 j + 13 k .
5 4 2
, ,
, , . . x = 0
Þ z = 3, .
, B (x o, y o, z o) (a 1, a 2, a 3), :
= =.
:
l: = =.
: p: 11 x + y 2 z = 0, l: = =.
11. :
x = 1 t, x = 3 + 2 t ¢,
l 1: y = 6 + 2 t, l 2: y = 2 3 t ¢,
z = 5 + 2 t, z = 3 2 t ¢.
, .
. : (1, 2, 2), (2,3,2) A (1, 6, 5)Î l 1 , B (3,2, 3) Î l 2 . :
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= =.
l 1 l 2. , l 1 l 2 , . , , , .
d =.
I j k
´ = 1 2 2 = 2 i + 2 j k; |´ |= = 3.
2 3 2
( 2, 8,2), = 22 82 2(1) = 18, d =.
= ´ . -, ^ l 1 ^ l 1, , . -: (2, 2,1). ,
h . π, l 1 h. , , A Îp.
x 1 y 2 z 1
1 2 2 = 0.
2 2 1
6(x 1) + 3( y 2) 6(z 1) = 0.
2(x 1) + ( y 2) 2(z 1) = 0.
p: 2 x + y 2 z + 2 = 0.
l 2 π . l 2 π:
2(3 + 2 t ¢) 2 + 3 t ¢ 2(3 2 t ¢) + 2 = 0,
6 4 t ¢ 2 3 t ¢ 6 4 t ¢ + 2 = 0,
7 t ¢= 0, t ¢= 0.
t ¢ l 2 , B (3,2, 3) l 2 π. h :
.
, h : π π1, l 2 . , .
. , . l 1 l 2:
h 2(t, t ¢) = (3 +2 t ¢ + 1 + t )2 + (2 3 t ¢ 6 2 t)2 + (3 2 t ¢ 5 2 t)2 =
= (t +2 t ¢ 2)2 + (8 + 2 t + 3 t ¢)2 + (2 + 2 t + 2 t ¢)2 .
h 2(t, t ¢). :
h 2(t, t ¢) = 2(t +2 t ¢ 2) + 4(8 + 2 t + 3 t ¢) + 4(2 + 2 t + 2 t ¢) = 2(9 t +12 t ¢ + 18);
h 2(t, t ¢) = 4(t +2 t ¢ 2) + 6(8 + 2 t + 3 t ¢) + 4(2 + 2 t + 2 t ¢) = 2(12 t +17 t ¢ + 24);
9 t +12 t ¢ + 18 = 0 t = 2
12 t +17 t ¢ + 24 = 0 t ¢ = 0.
t t ¢ l 1 l 2 , C (1, 2, 1) B (3,2, 3) . , B C.
12. S:
x 2 + y 2 + z 2 +12 x -10 y 4 z -176 = 0.
) p, A (3, 7, 1), B (1, 9, 2), C (3, 6, 6)
) , p S.
. : (2, 1, 1), (0,1, 5). , A (x o, y o, z o) (a 1, a 2, a 3), (b 1, b 2, b 3)
x x o y y o z z o
a 1 a 2 a 3 = 0.
b 1 b 2 b 3
:
x + 3 y 7 z 1
2 2 1 = 0.
0 1 5
:
O ¢ . :
(x 2 12 x + 36) 36 + ( y 2 +10 y + 25) + (z 2 + 4 z + 4) 4 176 = 0,
(x 6)2 + (y 5)2 + (z + 2)2 = 241.
, O ¢(6,5,2), R =.
, , , . , (11,10,2) . . , A (x o, y o, z o) (a 1, a 2, a 3)
x = x o + a 1 t ,
y = y o + a 2 t ,
z = z o + a 3 t .
:
x = 6 + 11 t ,
l: y = 5 10 t ,
z = 2 2 t .
. p. p. l π:
11(6 + 11 t) 10(5 10 t) 2(2 2 t) + 105 = 0,
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66 + 121 t + 50 + 100 t + 4 + 4 t + 105 = 0,
225 t = 225, t = 1.
t l : O ²(5, 5, 0). O ¢ O ² :
½ O ¢ O ²½= = 15.
r 2 = R 2 ½ O ¢ O ²½2 = 241 225 = 16.
, r = 4 .
: r = 4, O ²(5, 5, 0).