已知2cos^2a+3cosasina-3sin^2a=1.求tana.
求(1)tana；（2）2sina-3cosa/4sina-9cosa.
人气：344 ℃ 时间：2020-04-21 14:18:24
解答
因为 2cos^2a+3cosasina-3sin^2a=1=cos^2a+sin^2a
所以 原式为
cos^2a+3cosasina-4sin^2a=0
(cosa+4sina)(cosa-sina)=0
因此 cosa=-4sina,即 tana= -1/4
cosa=sina,即 tana=1
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