cos方(α-π/4)-sin方(π/4-α)得到

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cos方(α-π/4)-sin方(π/4-α)得到
cos方(α-π/4)-sin方(π/4-α)得到

cos方(α-π/4)-sin方(π/4-α)得到
[cos(α-π/4)]^2-[sin(π/4-α)]^2
=cos2(π/4-α)
=cos(π/2 -2α)
=sin2α

=cos方(π/4-α)-sin方(π/4-α)=cos方[2x(α-π/4)]=cos(2α-π/2)=sin2α
懂?