()
. () . , . .
.
288 3.
.
V = d3 / 6
288 = d3 / 6
d3 = 1728
d3 = 1728
d = 12
. 12
.
, R, H, . . , , , ?
.
. .
, .
:
r = S / p,
S -
p -
, . , , - ,
S = RH
p = 1/2 (2R + 2m)
m -
R - ,
m m = √(H2 + R2),
p = 1/2 (2R + 2√(H2 + R2)) = R + √(H2 + R2)
:
. ( , ). , - . " " sqrt(), sqrt - , . "√".
, l, 60 . .
.
:
S = 4πr2
, , . 60 , - ( - 180 , (180-60) / 2 = 60, ).
, . l.
R = √3/3 l
S = 4π(√3/3 l)2
S = 4/3πl2
: 4/3πl2.
(). 46 . 1 300 . , ?
.
.
, :
L = 2πR
R = L / 2π
R = 46 / 2π
R = 23 / π
|
|
S = πR2
S = π (23/π) 2
S = 529 / π
:
S = 4πr2
S = 4πr2 / 2
S = 2π (23/π) 2
S = 1058 / π
:
529 / π + 1058 / π = 1587 / π
(, , , 10 000 )
1587 / π * 300 / 10 000 = 47,61 / π ≈ 15,15
. ( ). , - . " " sqrt(), sqrt - , .
12 45 . .
.
, , , , , - .
, 45 (180 - 90 - 45).
, , , , . , .
d2 + d2 = 122
2d2 = 144
d2 = 72
V = d2 / 4 h
V = 72 / 4 * sqrt(72)
V = 18 * sqrt(72)
: 18 * sqrt(72)
. , 2, 60 . 45 . .
.
:
V = R2h
:
R - ,
h - .
. 1- .
, , . , :
R = a / 2 sin α
:
a -
α - , .
. , 180-90-60 = 30 . , ( ) :
R = 2a / 2 sin 30 = 2a
. 2-
. .
, :
2R = 2a / cos 60 = 2a / 0.5 = 4a
R = 2a
.
, , - , .
|
|
45 , 180 - 45 - 90 = 45 .
, , . :
V = R2h
V = *4a2*4a
V = 16a3.
: 16a3.
. ( ). , - . " " sqrt(), sqrt - , . "√".
.
, 17 , 15 ., 5 .
?
.
. , BM . BMK - . , MK = BC.
BK2 = BM2 + MK2
MK2 = BK2 - BM2
MK2 = 172 - 152
MK2 = 64
MK = 8
, MK = BC = 8
, . .
( , ).
AD - , , . BC - , , . ABCD - . , . , ABCD - . , .
.
AD = 2R = 2 * 5 = 10
OC = OD = R = 5
, , , , - . ,
AN = DP = (10 -8) / 2 = 1
OP = OD -DP = 5 - 1 = 4
CPO - , CP - .
CP2 + OP2 = OC2
CP2 = OC2 - OP2
CP2 = 52 - 42
CP2 = 25 - 16
CP = 3
: 3 .
( 2)
. ( ). , - . " " sqrt(), sqrt - , . "√".
.
- , 4√2.
.
.
- , a.
a2 + a2 = (4√2)2
2a2 = 32
a2 = 16
a = 4
:
V = πd2 / 4 * h
V = π42 / 4 * 4
V = 16π
: 16π
.
. .
.
.
. , AC ABCD
CD2 + AD2= AC2
a2 + a2 = AC2
2a2 = AC
AC = a√2
AC. , a√2.
, :
S = a * a√2 = a2√2
|
|
: a2√2
. ( ). , - . " " sqrt(), sqrt - , .
.
, , 8, 30 .
.
AC = 8 , ACD = 30,
CD = AC cos 30
. ACD - . , CD / AC = cos ∠ACD . cos 30 .
CD = 8 * √3/2 = 4√3
,
AD = AC sin 30
AD = 8 * 1/2 = 4
4/2 = 2
, ,
S1 = πR2 = 4π
- . :
S2 = 2πRh = 2π * 2 * 4√3 = 16π√3
:
S1 + S2 = 4π + 16π√3
: 4π + 16π√3