化简 sina3a/sina-cos3a/cosa

来源:学生作业帮助网 编辑:六六作业网 时间:2024/12/25 09:36:58
化简sina3a/sina-cos3a/cosa化简sina3a/sina-cos3a/cosa化简sina3a/sina-cos3a/cosasin3a=sin(2a+a)=sin2acosa+co

化简 sina3a/sina-cos3a/cosa
化简 sina3a/sina-cos3a/cosa

化简 sina3a/sina-cos3a/cosa
sin3a=sin(2a+a)=sin2acosa+cos2asina
=2sinacosa*cosa+cos2asina
所以sin3a/sina=2(cosa)^2+cos2a
cos3a=cos(2a+a)=cos2acosa-sin2asina
=cos2acosa-2sinacosa*sina
所以cos3a/cosa=cos2a-2(sina)^2
所以原式=2(cosa)^2+cos2a-[cos2a-2(sina)^2]
=2(cosa)^2+2(sina)^2
=2[(cosa)^2+(sina)^2]
=2