f(x)=cos(2x-兀/3)+2sin(x-兀/4)sin(x+兀/4)怎么化简

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f(x)=cos(2x-兀/3)+2sin(x-兀/4)sin(x+兀/4)怎么化简
f(x)=cos(2x-兀/3)+2sin(x-兀/4)sin(x+兀/4)怎么化简

f(x)=cos(2x-兀/3)+2sin(x-兀/4)sin(x+兀/4)怎么化简
积化和差
f(x)=cos(2x-π/3)+2sin(x-π/4)sin(x+π/4)
=cos(2x-π/3)+2×(-1/2){cos[(x-π/4)+(x+π/4)]-cos[(x-π/4)-(x+π/4)]}
=cos(2x-π/3)-[cos2x-cos(-π/2)]
=cos(2x-π/3)- cos2x
=cos2xcos(π/3)+sin2xsin(π/3) - cos2x
=(1/2)cos2x + (√3/2)sin2x - cos2x
=(√3/2)sin2x - (1/2)cos2x
=sin(2x-π/6)

和差化积、积化和差
被角公式