解ï¼
ç±æ£å¼¦å®çå¾a/sinA = c/sinC
åA=2C
â´a/sin2C = c/sinC
â´cosC= a/2c.
å2b=a+c=8
â´cosC=(a²+4²-c²)/8a
=[(a+c)(a-c)+16]/8a
=(a -c +2)/a
=(4a -4c +8)/4a
=(4a -3c +8-c)/4a
=(5a-3c)/4a
= a/2c
ä»è4a²=2cï¼5a -3cï¼=2ï¼5ac-3c²ï¼
2 a²-5ac+3c²=0
(2a-3c)(a-c)=0
âµå
è§A>B>C
â´aâ cå³a-câ 0
â´2a=3c
ä¸a+c=8èç«è§£å¾
a=24/5 c=16/5 .
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