soofuk

post 左 *8 高手睇睇

[ 本帖最後由 soofuk 於 2011-5-14 09:17 AM 編輯 ]

charityho

cos 1 + cos 179 = cos 1 + cos(180-1) = cos 1 - cos 1 = 0

cos 1 + cos2 +...+ cos179+cos180 = 0 + cos 90 + cos180 = -1

similar for Q2

william011894

11同15好似錯左

nikki219

假設本身tan x係60度既..
tan1/4x既 x值係15度..
姐係圖成個橫縮成原本既1/4..
你個圖又吾寫條方程,, 都吾知你岩吾岩-0-

桃子

Your graphs are clearly wrong.

y=tan x passes through (45 deg, 1).
y=2 tan x passes through (45 deg, 2).

y=tan x has a period of 180 deg.
y=tan (x/4) has a period of 45 deg.

soofuk

引用:

原帖由 charityho 於 2011-5-10 06:06 PM 發表
cos 1 + cos 179 = cos 1 + cos(180-1) = cos 1 - cos 1 = 0

cos 1 + cos2 +...+ cos179+cos180 = 0 + cos 90 + cos180 = -1



similar for Q2

下面點解有cos90  都係唔係幾明

soofuk

引用:

原帖由 nikki219 於 2011-5-10 07:27 PM 發表
假設本身tan x係60度既..
tan1/4x既 x值係15度..
姐係圖成個橫縮成原本既1/4..
你個圖又吾寫條方程,, 都吾知你岩吾岩-0-

引用:

原帖由 桃子 於 2011-5-10 09:17 PM 發表 [url=redirect.php?goto=findpost&pid=3302992&ptid=171912][/url]
Your graphs are clearly wrong.

y=tan x passes through (45 deg, 1).
y=2 tan x passes through (45 deg, 2).

y=tan x has a period of 180 deg.
y=tan (x/4) has a period of 45 deg.

唔該晒 我改返

引用:

原帖由 charityho 於 2011-5-10 06:06 PM 發表 [url=redirect.php?goto=findpost&pid=3302141&ptid=171912][/url]
cos 1 + cos 179 = cos 1 + cos(180-1) = cos 1 - cos 1 = 0

cos 1 + cos2 +...+ cos179+cos180 = 0 + cos 90 + cos180 = -1

similar for Q2

我研究到了

[ 本帖最後由 soofuk 於 2011-5-10 10:44 PM 編輯 ]

soofuk

更新一題


37 a  90,180 ,270 ,360 都係0 wo
咁b題 點 判斷方程既解 要考慮d咩因素先知道呢??

桃子

Draw the line y=1 and count the number of intersection.

soofuk

引用:

原帖由 桃子 於 2011-5-13 08:46 PM 發表
Draw the line y=1 and count the number of intersection.

我想證實下題a有冇錯 . 因為我d功課一交阿sir就有排先派 我想肯定自已既答案  等我可以考試前重溫


45度=3
135=-3
225=3
315=-3

如果根據上面結果 在y=1畫直線 應有4個解

桃子

It looks right.

For part (c), just read the intersection from the graph.

soofuk

引用:

原帖由 桃子 於 2011-5-13 10:07 PM 發表
It looks right.

For part (c), just read the intersection from the graph.

關於

ｃ題　
１／３ｓｉｎ２＝ｘ　
ｘ＝９．５５１
但書入面９．７４　　

桃子

In any graphical question, small errors will be allowed.

soofuk

thank you

桃子

As a note, this question may also be solved exactly.

3 sin 2x = 1
sin 2x = 1/3
.....

Even in graphical question, you may solve algebraically as a check.