,
.
, , , 138, 44, 52, 126 ?
.
, , , : " 180 ". : " 180 " " , , 180 ".
, 138 52, 44 126 . , 180 .
44 + 126 = 170
138 + 52 = 190
, .
:
.
32 24. .
.
, . .
. , , :
d 2 = 322 + 242
d 2 = 1600
d = 40
, , R = 40 / 2 = 20
: 20 .
. , 1,2,4,5 . . : n- 180(n-2). , : 180(n-2)=180*(4-2)=360 x, : x, 2x, 4x, 5x. | . , 1,2,4,5 г. . : n- 180(n-2). , : 180(n-2)=180*(4-2)=360 x, : x, 2x, 4x, 5x. |
, : x+2x+4x+5x=360, 12x=360 x=30 , 60, 120 150 . | , : x+2x+4x+5x=360, 12x=360 x=30 ³, 60, 120 150 . |
: 30, 60, 120, 150 . | ³: 30, 60, 120, 150 . |
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. ( ). , - . √ sqrt(), .
ABCD, B 60, AC 10,5 .
.
AC , , ABC - . ABC ACB ( ).
180 , (180 - 60) / 2 = 60.
, , . , AB = BC = AC.
, . P = 10,5 * 4 = 42
: 42
ABCD BD 14 , AC 48 .
.
,
DO = OB = BD / 2
DO = OB = 24
AO = OC = AC /2
AO = OC = 7
, , AOD AOB - .
AO2 + OB2 = AB2
72 + 242 = AB2
49 + 576 =
625 = AB2
AB =25
: 25
( ) .
́ ( .-. τραπέζιον ; τράπεζα , ) , .
- , .
. .
a b -
c d -
m -
r -
S -
( )
. , - .
BD AC ABCD O. BD 40 . D, BC AD 3 7.
.
AOD BOC - AOD BOC , , .
, , 3 7. :
BO / OD = 3 / 7
, BO + OD = 40,
OD = 40 - BO
,
BO / (40 - BO) = 3 / 7
7BO = 3 (40 - BO)
7BO = 120 - 3BO
10BO = 120
BO = 12
, OD = 40 - 12 = 28
: 28
4 , 10 . .
.
, b. :
|
|
:
a - b = 4
(a + b) / 2 = 10
a = b + 4,
(b + 4 + b) / 2 = 10
2b + 4 = 20
b = 8
a = b + 4 = 12
: 8 12
( )
. . , - .
.
ABCD (AD | | ) . , D = 24 , = 9, = 6 .
.
.
AOD BOC - AOD BOC , , .
, , AO OC.
AO / OC = AD / BC
9 / 6 = 24 / BC
BC = 24 * 6 / 9 = 16
: 16
.
ABCD , AD=24, =8, =13, BD=5√17. .
.
B C . - AM = a, KD = b ( ). , , , MBCK - .
AD = AM+BC+KD
a + 8 + b = 24
a = 16 - b
DBM ACK - , . h.
h2 + (24 - a)2 = (5√17)2
h2 + (24 - b)2 = 132
, a = 16 - b,
h2 + (24 - 16 + b)2 = 425
h2 = 425 - (8 + b)2
, . :
425 - (8 + b)2 + (24 - b)2 = 169
-(64 + 16b + b)2 + (24 - b)2 = -256
-64 - 16b - b2 + 576 - 48b + b2 = -256
-64b = -768
b = 12
, KD = 12
h2 = 425 - (8 + b)2 = 425 - (8 + 12)2 = 25
h = 5
, a b - , h -
S = (24 + 8) * 5 / 2 = 80 2
: 80 2.
. ( ). , - . " " sqrt(), sqrt - , . "√"
, 12 . , .
.
ABCD. a ( AD) b ( BC). ∠A.
, ,
S = ab
C ABCD CK. . ,
CK2 + KD2 = CD2
, CD = a + b
, , AD = AK + KD. , ABCK, BC = AK = b, , KD KD = a - b.
122 + (a - b)2 = (a + b)2
144 + a2 - 2ab + b2 = a2 + 2ab + b2
144 = 4ab
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S = ab (. ),
144 = 4S
S = 144 / 4 = 36
: 36 2.