www.fltk.net > Cos80°Cos35°+Cos10°Cos55°=______

Cos80°Cos35°+Cos10°Cos55°=______

∵cos80°cos35°+cos10°cos55°=cos80°cos35°+sin80°sin35°=cos(80°-35°)=cos45°= 2 2 .故答案为: 2 2 .

原式=sin80º•sin(90º-35º) + cos80º•sin35º =sin80º•cos35º + cos80º•sin35º =sin(80º+35º) =sin115º =sin(90º+25º) =sin25º

cos80°cos35°+cos10°cos55° =sin10°cos35°+cos10°sin35° =sin(10+35)° =sin45° =√2/2

sin80°cos35°-sin10°cos55°=sin(90°-10°)cos35°-sin10°cos(90°-35°)=cos10°cos35°-sin10°sin35°=cos(10°+35°)=cos45°= 2 2 .故答案为: 2 2

原式=cos80cos35+sin80sin35=cos(80-35)=cos45

80 = 90-10;130= 180-50;一化简,你就看出来了,结果:-根号(3)/2

原式=sin10cos50+cos10sin50 =sin(10+50) =sn60 =√3/2

不知道你是要求分开的值还是乘起来的值,如果是后者就简单了。 cos20°cos40°cos80° =2sin20°cos20°cos40°cos80°/2sin20° =sin40°cos40°cos80°/2sin20° =sin80°cos80°/4sin20° =sin160°/8sin20° =sin20°/8sin20° =1/8 谢谢望采纳

搞不懂就不用和差化积,用sin倍角公式,稍等

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