化简求值:2cosˆ210°-tan5°(1+cos10°)-2sin40°sin80°
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化简求值:2cosˆ210°-tan5°(1+cos10°)-2sin40°sin80°
2(cos10°)^2-tan5°(1+cos10°)-2sin40°sin80°
=cos20°+1-sin5°/cos5°*(1+2(cos5°)^2-1)-(cos(40°-80°)-cos(40°+80°))
=cos20°+1-2sin5°*cos5°-cos40°+cos120°
=cos20°-sin10°-cos40°+1/2
=cos20°-(cos80°+cos40°)+1/2
=cos20°-2*cos(60°)*cos20°+1/2
=cos20°-cos20°+1/2
=1/2
利用了正余弦的二倍角公式、积化和差、和差化积公式.
=cos20°+1-sin5°/cos5°*(1+2(cos5°)^2-1)-(cos(40°-80°)-cos(40°+80°))
=cos20°+1-2sin5°*cos5°-cos40°+cos120°
=cos20°-sin10°-cos40°+1/2
=cos20°-(cos80°+cos40°)+1/2
=cos20°-2*cos(60°)*cos20°+1/2
=cos20°-cos20°+1/2
=1/2
利用了正余弦的二倍角公式、积化和差、和差化积公式.
求值:2sin50°+sin80°(1+3tan10°)1+cos10°
求值:(2sin80°-cos70°)/cos20°
求值[2sin50°+sin10°(1+√3tan10°)]*√2(sin80°)*(sin80°)
化简三角函数sin40°(sin10°-√3cos10°)化成sin乘cos的形式,请写出思考过程,
2sin50度.sin40度 /cos10度为什么等于sin80度/cos10度?为什么又等于1?
求值:[2sin50°+sin10°(1+√3tan10°)]×√2sin80°
求值:[2sin50°+sin80°(1+√3tan10°)]/√2cos5°
sin40°cos10°-cos40°sin10°
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化简:(1).1/sin10°-根号3/cos10° (2).sin40°(tan10°-根号3) (3).tan70°
求值:1/sin10°-根号3/sin80°
求值:1/sin10°-√3/sin80°