cos80°cos20°+sin100°sin380°=?

cos80°cos20°+sin100°sin380°=? cos20°-cos40°-cos80°= cos20°cos40°cos80°=? 计算cos20°cos40°cos80° 化简cos20°cos40°cos60°cos80° cos20°*cos40°*cos60°*cos80°= cos20°cos40°cos60°cos80°是多少 不查表求:cos20°*cos40°*cos60°*cos80°= cos20°cos10°-cos70°cos80° 化简cos20°-cos40°-cos80°等于? cos20°cos40°cos80°怎么算 cos20°cos40°cos80°的值、急 cos20°-cos40°-cos80°的值为? cos20°cos40°cos80°的值是 计算cos20°cos40°cos80°=多少 cos20°×cos40°×cos80°=______ cos20°+cos40°+cos80°=______ cos100°cos20°-sin100°sin20° 怎么算啊