(sin20°+2sin40°)/cos20°不用和差化积公式,

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(sin20°+2sin40°)/cos20° 不用和差化积公式,

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答案和解析

(sin20°+2sin40°)/cos20°
=(sin20°+2cos50°)/cos20°
=(sin20°+2cos(20+30)°)/cos20°
=(sin20°+根3cos20°-sin20°)/cos20°
=根3

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