[解題]高中數學複數

看板tutor作者 (最愛寶寶)時間17年前 (2008/08/22 17:01), 編輯推噓2(2推 0噓 5→)
留言7則, 1人參與, 最新討論串1/1
w=cos2π/5 + icos2π/5 ,在複數平面上A(1),B(w1),c(w2),D(w3) ,E(w4) 試求: (1)ＡＢ．ＡＣ．ＡＤ．ＡＥ＝5 (2)sin36．sin72．sin108．sin144=5/16 第一題ok 第二題why?? 請高手幫忙解答囉 -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 140.128.195.241
推
08/22 17:34, , 1F
math版 16183 找不到的話找我id 三角函數那篇
08/22 17:34, 1F
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08/22 17:34, , 2F
用複數姐三角連乘
08/22 17:34, 2F
推
08/22 17:47, , 3F
用我那篇的概念的話題目可寫為
08/22 17:47, 3F
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08/22 17:47, , 4F
sin(π/5)*sin(2π/5)*sin(3π/5)*sin(4π/5) =
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08/22 17:48, , 5F
[sin(π/5)*sin(2π/5)]*[sin(π/5)*sin(2π/5)]
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08/22 17:48, , 6F
= (√5/4)*(√5/4) = 16/5
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08/22 17:49, , 7F
... 5/16
08/22 17:49, 7F
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