cos20°+cos100度+cos140度=?

cos20°+cos100度+cos140度=? cos20°-sin40°+cos60°+cos100° cos20度+cos60度+cos100度+cos140度=? cos20度+cos100度-cos40度等于多少求过程 cos20+cos60+cos100+cos140求值 (cos80°-cos20°)/sin80°+sin20°)=顺便再回答个cos20°+cos100°+cos140°= cos20°—cos40°+cos60°+cos100°的值答案为1/2 cos100°cos20°-sin100°sin20° 怎么算啊 cos20°+cos100°+cos140°=?我们只学过 和角差角公式...汗.. 化简cos20度+cos100度+cos140度 为什么答案是0 cos100度, 数学cos20+cos60+cos100+cos140=?如题过程 (cos20)∧4+(cos100)∧4+(cos140)∧4 设M＝cos20°×cos40°×cos60°×cos80°×cos100°×cos120°×cos140°×cos160°,求证：M＝1/256 已知logaX=1/cos20°,logbX=1/cos60°,logcX=1/cos100°,logdX=1/cos140°,求logabcdX的值 我想要问一道关于三角函数的题,希望能尽快解答Cos20°+ Cos 60°+ Cos100°+ Cos140°=? cos100°的绝对值等不等于-cos100° 求值 1/cos100°^2-3/cos100°^2