sin80°/cos10°的值是多少?
来源:学生作业帮 编辑:作业帮 分类:数学作业 时间:2024/05/23 23:00:42
sin80°/cos10°的值是多少?
用到积化和差公式和倍角公式
sinαsinβ=-[cos(α+β)-cos(α-β)]/2
cos^2 α=1/2(1+cos2α)
sin^2 40°+cos^2 10°-sin40°sin80°
=cos^2 50°+cos^2 10°+1/2[cos (40°+80°)-cos(40°-80°)
=1/2(1+cos100°)+1/2(1+cos20°)+1/2[cos (40°+80°)-cos(40°-80°)
=1+1/2(cos100°+cos20°)+1/2(cos120°-cos40°)
=1+1/2(cos100°+cos20°)-1/4-1/2cos40°
=3/4+cos60°cos40°-1/2cos40°
=3/4
sinαsinβ=-[cos(α+β)-cos(α-β)]/2
cos^2 α=1/2(1+cos2α)
sin^2 40°+cos^2 10°-sin40°sin80°
=cos^2 50°+cos^2 10°+1/2[cos (40°+80°)-cos(40°-80°)
=1/2(1+cos100°)+1/2(1+cos20°)+1/2[cos (40°+80°)-cos(40°-80°)
=1+1/2(cos100°+cos20°)+1/2(cos120°-cos40°)
=1+1/2(cos100°+cos20°)-1/4-1/2cos40°
=3/4+cos60°cos40°-1/2cos40°
=3/4
求值:2sin50°+sin80°(1+3tan10°)1+cos10°
sin80度为什么等于cos10度怎样推导的呢
1/sin10°-根号3/sin80°的值为
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已知tan100°=k,则sin80°的值等于______.
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1/sin10°-根号3/sin80°
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三角函数恒等变换1/sin10° -根号3/sin80的值为如果比较麻烦也可以直接写思路
化简:cos10°tan20°