æä¸è§å½¢è¡¥æå¹³è¡å边形ABCE,AC,BE为对è§çº¿,
é£ä¹
ç±ä½å¼¦å®çæ
BE^2=BC^2+CE^2-2BC*CE*cosè§BCE (è§BCEä¸è§Bäºè¡¥)
20=BC^2+32/3-2*BC*4â6/3*(-â6/6)
20=BC^2+32/3+BC*8/3
3BC^2+8BC-28=0
(3BC+14)(BC-2)=0
æ以
BC=2
åç±ä½å¼¦å®çå¾
AC^2=BC^2+AB^2-2BC*AB*cosè§B
=4+32/3-2*2*4â6/3*(â6/6)
=28/3
æ以
AC=2â21/3
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BC/sinA=AC/sinB
sinB=â1-(â6/6)^2=â30/6
2/sinA=(2â21/3)/(â30/6)
æ以
sinA=â70/14
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