cos140°cos20°-sin220°sin20°

cos140°cos20°-sin220°sin20° cos140°cos20°-sin220°sin20° cos140°cos20°-sin220°sin20° 若cos140°=a,则sin220的值为? cos20°+cos100度+cos140度=? 化简cos20° cos140° cos260°=---急用! (cos80°-cos20°)/sin80°+sin20°)=顺便再回答个cos20°+cos100°+cos140°= cos20°+cos100°+cos140°=?我们只学过 和角差角公式...汗.. cos20+cos60+cos100+cos140求值 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°=? cos140°=a tan40°= sin140度cos20度-cos140度cos70度化简求值 cos20度+cos60度+cos100度+cos140度=? 数学cos20+cos60+cos100+cos140=?如题过程 (cos20)∧4+(cos100)∧4+(cos140)∧4 tan20°+ cos20