若tanα=m,求sin(-6π-α)cos(4π+α)的值
人气:318 ℃ 时间:2020-04-08 22:16:57
解答
sin(-6π-α)cos(4π+α)=sin(-a) cosa= -sina cosa
=(-sina cosa)/ ((sina)^2+(cosa)^2) (分子分母同时除cosa*cosa)
得到:= -tana/(tana*tana+1)= -m/(m*m+1)
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