白_痴
幼苗
共回答了21个问题采纳率:81% 举报
①当n=2k时,
f(x) =-sinxcosx/(-cosx)·(1/tanx)
=-cosx
f(7π/6)=√3/2
②当n=2k+1时,
f(x)=sinx·(-cosx)/cosx·(1/tanx)
=-cosx
f(7π/6)=√3/2
∴当n∈Z时,f(7π/6)=√3/2
1年前
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白_痴
改正一下,当n=2k,f(7π/6)=cos7π/6=-√3/2
当n=2k+1,f(7π/6)=-cos7π/6=√3/2
∴当n∈Z,f(7π/6)=±√3/2