一條中4數唔識計-'
回答 (3)
2010-04-01 7:21 am
✔ 最佳答案
sinX-cosX=1/4(sin X - cos Y)^2 = (1/4)^2
(sin X)^2 - 2sinX ．cosX + (cos Y)^2 = 1/16
(sin X)^2 + (cos Y)^2 - 2sinX ．cosX = 1/16
1 - 2sinX cosX = 1/16
1 - 1/16 = 2sinX cosX
15/16 = 2sinX cosX
sinX cosX = 15/32
2010-03-31 23:22:35 補充：
Typing error :
Y should be X
2010-04-05 7:36 am
sinX - cosX = 1/4
(sinX - cosX)^2 = 1/16
(sinX)^2 - 2sinXcosX + (cosX)^2 = 1/16
-2sinXcosX = 1/16 - 1
sinXcosX = 15/32
Note : cosX ^2 + sinX ^2 =1
(sinX - cosX)^2 = 1/16
(sinX)^2 - 2sinXcosX + (cosX)^2 = 1/16
-2sinXcosX = 1/16 - 1
sinXcosX = 15/32
Note : cosX ^2 + sinX ^2 =1
2010-04-04 1:31 am
收錄日期: 2021-04-21 22:09:31
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20100331000051KK01693