【贴子恢复】如何恢复被删除的贴子

贴吧意见反馈吧

tid:52149884942017/07/10 15:57:45

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楼主：贴吧阿Sir

最后回复：koinchange

2025/07/05 19:04:26

5284楼

pid:1180334179482018/02/13 19:09:40

司马骧苴

申请恢复：用的是正弦定理和二倍角公式：sinB cosc =- sinB(cos(B+A) =sinA (cosB)^2+sinBcosACOSB=-sinBCOSBCOSA+(sinB)^2sinA=sinA (cosB)^2+sinB cosA cosB=sinA[(COSb)^2-(SinB)^2]=2sinBcosBcosA-sinA COS2B=sinB COSA,-tanA=tan2B,-A=2B,2B+A=0,sin(2B+A)=0,2B+A=π,A+B+C=π.B-C=0,B=C.