(1)3cOS(b-c)-1=6cosbcosc,簡化為3(cosbcosc sinbsincc)-1=6cosbcosc,變形為3(cosbcosc-sinbsincc)=-1,即cos(B C)=-1/3,則cosA=-cos(B C)=1/3∴sinA=根號1-cos2A=2根號2/3(2)∫cosa=1/3Sina=2根號2/3,S△ABC=2,團隊會回答你的問題。
(1)3c OS(b-c)-1 = 6 cosbcosc,簡化為3(cosbcosc sinbsincc)-1 = 6 cosbcosc,變形為3 (cosbcosc-sinbsincc) =-1,即cos(B C)=-1/3,則cosA=-cos(B C)=1/3∴sinA=根號1-cos2A=2根號2/3(2)∫cosa = 1/3 Sina = 2根號2/3,S△ABC=2。團隊會回答你的問題。不懂可以提問!如果你同意我的答案
1。y = 2 2-5 sinx-4 =-2 2-5 sinx-2 =-2 2 9/8 from-1。
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