已知tan a=-1/3,求4sin a-2cos a/5cos a+3sin a=

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已知tan a=-1/3,求4sin a-2cos a/5cos a+3sin a=
已知tan a=-1/3,求4sin a-2cos a/5cos a+3sin a=

已知tan a=-1/3,求4sin a-2cos a/5cos a+3sin a=
(4sin a-2cos a)/(5cos a+3sin a)=(4tana-2)/(5+3tana)=(-4/3-2)/[5+3(-1/3)]
=(-10/3)/4=-10/12=-5/6