作者wayne2011 (今年十三号星期五)
看板Math
标题Re: [中学] 三角函数
时间Thu Oct 19 10:38:16 2017
※ 引述《wayne2011 (今年十三号星期五)》之铭言：
: ※ 引述《Honor1984 (奈何上天造化弄人？)》之铭言：
: : sin(b)
: : ------------
: : sin(a)sin(r)
: : 2△CDE CA CD CB CE
: : = ------------------------------
: : 2△CAD 2△CBE CD CE
: : = (3/2) (11/6)
: : = 11/4
: 原式
: =cos(gamma+alpha)/[sin(gamma)*sin(alpha)]
: =cot(gamma)cot(alpha)-1 连比例
: 6/5=BCsin(gamma)/CAsin(alpha+beta)...分定 BE:DE:DA = 6:3:2
: 6/5=BCsin(gamma)/CAcos(gamma)...正余弦互换 2 1
: cot(gamma)=5BC/6CA,同理,cot(alpha)=9CA/2BC. 3 2
: =(15/4)-1=11/4...ans
参考"标准奥数教程(初三分册)"
习题2.1的4th题
2*6/(2+3)(3+6)=sin(gamma)sin(alpha)/cos(gamma)cos(alpha)
cot(gamma)cot(alpha)=15/4...此题为证明
--
※ 发信站: 批踢踢实业坊(ptt.cc), 来自: 61.58.103.35
※ 文章网址: https://webptt.com/cn.aspx?n=bbs/Math/M.1508380698.A.38F.html
1F：推 JI1 : how do you understand the origin? 10/19 10:41
2F：推 JI1 : and how do you understand the number zero? 10/19 10:43
3F：→ wayne2011 : i don't know~maybe still have a long time to go~ 10/19 10:43
4F：推 JI1 : how do you understand the beginning...?:) 10/19 10:44