4
. (. .): AB = BC ; AC . . (. .): A 1B 1 = B 1C 1 = A 1C 1 . , . | ||
: ; , , ;
AB = BC ( ), AO = OC (BO ), BO ABO CBO. ABO = CBO 3- . : ABO = CBO. BO . AOC = 180. AOB = COB =
= 90. | ||
: , ; , ; , ; , . |
5
, .
, , .
ab , , a∥b.
!
, , , , .
:
1. . , .
, , .
, , , , .
- H c . , , .
, .
, .
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.
, , , .
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.
1. , .
2. , .
.
:
- ,
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- 180.
6
180.
.
KLM , ∡K+∡L+∡M=180.
L a, KM.
, 1, a KM KL, , 2 ML.
, 1, 2 3 L, . .
∡1+∡2+∡3= 180 ∡K+∡L+∡M=180.
.
1. 90.
2. 45.
3. 60.
4. , , .
5. , .
.
∡KML+∡BML= 180 ∡K+∡L+∡KML=180 , ∡BML=∡K+∡L.
,
, .
KLM .
KLM K=90.
, , , .
LN , LK KN .
KLM .
7
, ( 90˚).
, , .
, , .