化简2cos^2 α-1/2tan(π/4-α)sin^2(π/4+α)

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化简2cos^2α-1/2tan(π/4-α)sin^2(π/4+α)化简2cos^2α-1/2tan(π/4-α)sin^2(π/4+α)化简2cos^2α-1/2tan(π/4-α)sin^2(π

化简2cos^2 α-1/2tan(π/4-α)sin^2(π/4+α)
化简2cos^2 α-1/2tan(π/4-α)sin^2(π/4+α)

化简2cos^2 α-1/2tan(π/4-α)sin^2(π/4+α)
用a
原式=2cos²a-1/2sin(π/4-a)/cos(π/4-a)*cos²[π/2-(π/4+a)]
=2cos²a-1/2sin(π/4-a)/cos(π/4-a)*cos²(π/4-a)
=2cos²a-1+1-1/2sin(π/4-a)cos(π/4-a)
=cos2a+1-1/4*sin(π/2-2a)
=cos2a+1-1/4*cos2a
=3/4*cos2a+1