3????????,???18cm,??????2?,?????????___

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13.1.1????????
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1?(1)????????????? (2)??????
(3)????????? (4)?????????
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2?????,??????????????????,?????????????
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1????????????5,??7,???????___ 2????????????5,????
???? ___ 3????????,???18cm,??????2?,?????
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????ABC?,???????,????B?????????????C,??????
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???? ACBCgtAB,ABBCgtAC
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??????????????????????? (1)3cm?8cm?4cm (2)5cm?6
cm?11cm (3)5cm?0.6dm?10cm
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?1 (1)???????????3cm, ??????5cm,??????____cm
(2)????????????2cm???????5cm,??????____cm

?? ???????,???18cm,??????4cm,??????
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?2 ??????????? 3?a-2?5, (1)?a?????
(2)?a???,???????????
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13.1.2????????
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1.?????????????? 2.????????????? ???
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1???????????
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Rt ?ABC
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2?????????180
? ? 1.??ABC?,?A30,? B40 ,?? C
. 2.?Rt?ABC?,?A30,? B???,?? C
___ 3.??ABC?,?A ? B ? C ,??A ___
4.??ABC?,?A??B??C1?2?3,?????????????????
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• ?1.??????,?ABC?,BD?AC,
• ???D??ABD54,?DBC18?
• ??A??C????

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?2. (1)???????????70,?????????? (2)??????
?????100,??????????
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(1)????????? ???? (2)?????????
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13.1.3 ???????????
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2.????
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3.????
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1.????ABC??
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AD??ABC?BC????
AD?BC,???D
?ADB?ADC
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2.?????????
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3.???????????????
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?D?BC??? ?D?BC?,?BDDC
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? ?
1.??,??ABC?, ?1?2,G?AD??,??BG?AC?E,F?AB???
,CF?AD?H,????????????,??????.
A

?AD??ABE????? ( )
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?CH??ACD?AD??? ( )
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2.? ABC?,ABAC,????BC??????????
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?1.?ABC?,?C?ABC2?A,BD?AC???
?,??DBC????
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?2.?ABC?,ABAC,BD??ABC???,? ??ABC?????18cm?12cm???
???ABC?????
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