soofuk

計到一半禁唔倒機   ，未知是否上面步驟有錯呢 ??

圖中最後果個數就係答案

[ 本帖最後由 soofuk 於 2011-4-30 01:25 PM 編輯 ]

yeungwk91

點解要找sin,cos 數值?
直接
tan() -1/tan()
= ....

wtc123

認同

其實問題好簡單，唔好複雜化= =

yeungwk91

BTW , if 90<()<180
tan() < 0
Q is wrong?

桃子

There's nothing wrong with the question.

You are already given that tan x=2/sqrt(3), which is positive.

yeungwk91

sor
I mislook the range

However,
if tan >0 =>    180<()<270
so both sin and cos < 0
your steps are wrong

soofuk

咁(2/√3) - (1/2√3) 點計 √3/6

用筆算我唔識 用計數機出小數

yeungwk91

2/root3 = 2/root3 * root3/root3 = 2root3/3

桃子

(2 / √3) - (√3 / 2)
=(2/3) √3 - (1/2) √3
=(1/6) √3

soofuk

更新 ,有2題不明白
圈住就係答案
我邊一步做錯左 我有檢查過 自已計數步驟

各位請指正一下

edwincyy

上面果題
   cos0 * cos180 -√3 sin(-780)
= 1*-1 -√3 * (-sin60)
=  -1 - (√3 )*(-√3) / 2
= -1 +3/2
= 1/2

23條 tan(-225) = - tan225 = -1 =.="

soofuk

引用:

原帖由 edwincyy 於 2011-4-28 06:31 PM 發表
上面果題
   cos0 * cos180 -√3 sin(-780)
= 1*-1 -√3 * (-sin60)
=  -1 - (√3 )*(-√3) / 2
= -1 +3/2
= 1/2

23條 tan(-225) = - tan225 = -1 =.="

明
我初初以為 sin(-780) 變 sin780 之後 就sin60  原來我冇考慮到個象限  唔怪之得正負錯晒

[ 本帖最後由 soofuk 於 2011-4-30 01:25 PM 編輯 ]