cos100°cos40°+sin80°sin40°
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cos100°cos40°+sin80°sin40°cos100°cos40°+sin80°sin40°cos100°cos40°+sin80°sin40°cos100°=-cos80°cos(a+b
cos100°cos40°+sin80°sin40°
cos100°cos40°+sin80°sin40°
cos100°cos40°+sin80°sin40°
cos100°=-cos80° cos(a+b)=cosacosb-sinasinb
所以原式=sin80°sin40°-cos80°cos40°=-COS120°=1/2
不懂追问
cos100°cos40°+sin80°sin40°=cos100°cos40°+sin100°sin40°=cos（100°-40°）=cos60°=1/2
cos100=-cos80
所以 原式=-（cos80cos10-sin40sin80）=-cos(80+40)=1/2
cos100°cos40°+sin80°sin40°
化简cos100°cos40°+sin80°sin40°
sin40°cos40°=sin80°?
2cos40°sin40° 为啥等于sin80°呢?
(tan10°-根号3)*（sin80°/cos40°
cos20°—cos40°+cos60°+cos100°的值答案为1/2
cos100°-cos40°=（-sin70°）怎么从左边推算到右边的?
(cos80°-cos20°)/sin80°+sin20°)=顺便再回答个cos20°+cos100°+cos140°=
为何2cos40°sin40°/cos10°=sin80°/cos10°
cos40°cos80°+sin40°sin80°怎么算求详细过程
cos40°sin80°+sin40°cos80°等于多少请写清步骤哦~
cos100°-cos40°=（-sin70°）怎么从左边推算到右边的?需要具体的步骤
cos100°的绝对值等不等于-cos100°
求值 1/cos100°^2-3/cos100°^2
sin80°得多少
设M＝cos20°×cos40°×cos60°×cos80°×cos100°×cos120°×cos140°×cos160°,求证：M＝1/256
sin80=sin100.还是cos100
cos20°+cos100度+cos140度=?