tothenines
幼苗
共回答了12个问题采纳率:91.7% 举报
1.由a,b平行得:
3+y=(1-tanx)(1+sin2x+cos2x)=[(cosx-sinx)/cosx][2sinxcosx+2(cosx)^2]
=2(cosx-sinx)(sinx+cosx)=2cos2x
所以 y=2cos2x-3
2.f(a/2)-f(a/2+π/4)=2cosa-3-2cos(a+π/2)+3=2cosa+2sina=2根2sin(a+π/4)≥根6
=> sin(a+π/4)≥(根3)/2 => π/3≤a+π/4≤2π/3
=>π/12≤a≤5π/12
1年前
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