化简:sin方A+sin方(A-π/3)+sin方(A+π/3)

yang0jian 1年前 已收到1个回答 举报

七侠镇一姐 幼苗

共回答了16个问题采纳率:93.8% 举报

sin方A+sin方(A-π/3)+sin方(A+π/3)
=(1-cos2A)/2+(1-cos(2A-2π/3))/2+(1-cos(2A+2π/3))/2
=3/2-cos2A/2-[cos(2A-2π/3)+cos(2A+2π/3)]/2
=3/2-cos2A/2-cos2Acos4π/3
=3/2-cos2A/2+cos2A/2
=3/2

1年前

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