cosπ/9cos2π/9cos3π/9cos4π/9=?
1个回答
展开全部
原式=(sinπ/9cosπ/9cos2π/9cos3π/9cos4π/9)/sinπ/9,
=1/2(sin2π/9cos2π/9cos3π/9cos4π/9)/sinπ/9,
=1/4(sin4π/9cos3π/9cos4π/9)/sinπ/9,
=1/8(sin8π/9cos3π/9)/sinπ/9,
=1/8(sinπ/9cosπ/3)/sinπ/9,
(sin8π/9=sin(π-π/9)
=1/8cosπ/3,
=1/16
=1/2(sin2π/9cos2π/9cos3π/9cos4π/9)/sinπ/9,
=1/4(sin4π/9cos3π/9cos4π/9)/sinπ/9,
=1/8(sin8π/9cos3π/9)/sinπ/9,
=1/8(sinπ/9cosπ/3)/sinπ/9,
(sin8π/9=sin(π-π/9)
=1/8cosπ/3,
=1/16
已赞过
已踩过<
评论
收起
你对这个回答的评价是？
推荐律师服务：
若未解决您的问题，请您详细描述您的问题，通过百度律临进行免费专业咨询
