[超急]利用三角恆等式化簡三角式(4題20分!)

10 拆（）
（１－cos@)(1 cos@)
= 1-(cos@)(square)
=(sin@)(square) (this is sin@ 2次）

12 (sin@)square/ (1-(sin@)square)
= (sin@)square/ (cos@)square
=(sin@/cos@)square
=(tan@)square

14 你可以畫個３角形出黎
　13開方　／｜　２
　 　－－－
3
因sin@=正 tan@= 正
所以 cos= 正
所以cos =2/3

16 3- 2(cos@)square- 2(sin@)square
= 3-2[(cos@)square (sin@)square]
=1

2008-05-29 15:58:17 補充：
ｓｏｒｒｙ
１４　係３／（１３）開方

2008-05-29 15:59:04 補充：
你想像一下１４的那個是三角形～

http://i32.photobucket.com/albums/d50/pzsing/trisimm.jpg