sin2α=2/3,cos²(α+π/4)=?
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sin2α=2/3,cos²(α+π/4)=?
sin2α=2/3,cos²(α+π/4)=?
sin2α=2/3,cos²(α+π/4)=?
cos²(α+π/4)=(1+cos2(α+π/4))/2
=(1+cos(2α+π/2))/2
=(1-sin2α)/2
=(1-2/3)/2
=1/6