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sin(45°+α)sin(45°-α)=1/6,α∈(90°,180°),求sin4α
人气:357 ℃ 时间:2020-06-13 22:16:57
解答
sin(45°+α)sin(45°-α)=1/6∵sin(45°-α)=sin[90º-(45º+α)]=cos(45º+α)∴sin(45°+α)cos(45°+α)=1/6两边同时乘以22sin(45°+α)cos(45°+α)=1/3根据二倍角正弦公式:2sin(45°+α)cos(45°...
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