数学T paper 2讨论专区

ultikiller

第六题：常理来的，没记错课本上应该有写..我考试时都会直接用..假如把三角形每个角和对面的边画上一条线（ ...
Jacss 发表于 4-10-2010 01:57 AM

第六题：课本哪里才能找到那个三角形原理？

第七题：还是看不太懂。可以的话画出来比较明白。

wuhu

麻烦大家帮我解答下，我做了很久但是一直做不到答案～

If (a√2+b√3)2= 59 - 10√6 , find the values of a and b~

Allmaths

麻烦大家帮我解答下，我做了很久但是一直做不到答案～

If (a√2+b√3)2= 59 - 10√6 , find the va ...
wuhu 发表于 6-10-2010 06:24 PM

这题应该是在数学Paper 1讨论专区里的...
(a√2+b√3)^2=2a^2+3b^2+2ab√6


compare with 59 - 10√6,



2a^2+3b^2=59   --->eq 1
2ab=-10
a=-5/b   --->eq 2


然后sub eq 2 into eq 1 找b.

wuhu

这题应该是在数学Paper 1讨论专区里的...
(a√2+b√3)^2=2a^2+3b^2+2ab√6


compare with ...
Allmaths 发表于 6-10-2010 06:37 PM

   不好意识啊刚才看错了所以放到来这里问～谢谢你啦～

數學神童

find the values of x for the equation (tan x)^2=cos2x

blazex

Halim has to leave the office to go to the post office, the bookshop, and the bank. The time, in minutes, spent on these three places are normal random variables A~N(15,4), B~N(5,1) and C~N(8,2) respectively. D~N(12,3) is the time spent walking to all the three places and then back to the office. Assume all four times are normal distribution and he plans to leave the office at 0900. He also intends to post a note on the door which reads"I will return by----"What time, to the nearest minute, should Halim write on the note if he wants the probability of returning after the time to be less than 0.01%?

我是算到0947， 但是答案是0948？

peaceboy

回复 427# blazex


   因为它的probability是少过0.01，如果你拿0947就多过0.01一点点了
所以这种问题进位要小心....不是四舍五入的...

blazex

何谓四含五入？难道是指X<47.4的时候就是X的最小数值是48？

peaceboy

何谓四含五入？难道是指X
blazex 发表于 10-10-2010 01:36 PM

四舍五入就是round off的意思
你最后拿到47.4的意思是x多过47.4的时候Probability 少过0.01
所以如果你拿47罢了probability就多过0.01了
所以拿48...

Jacss

find the values of x for the equation (tan x)^2=cos2x
數學神童 发表于 8-10-2010 03:11 PM

(tan x)^2=cos2x(sin x)^2 / (cos x)^2 = 2(cos x)^2 -1
(sin x)^2 = 2(cos x)^4 - (cos x)^2
(sin x)^2 + (cos x)^2 = 2(cos x)^4
1 = 2(cos x)^4
1/2 = (cos x)^4
...
x=32.77" or 327.23"

Long time din do trigo questions, hope this will correct..

ultikiller

求解。

Given that sin (x+y) = p cos(x+y), show that tan x = p - tan y/1 - p tan y

Allmaths

求解。

Given that sin (x+y) = p cos(x+y), show that tan x = p - tan y/1 - p tan y
ultikiller 发表于 11-10-2010 07:43 PM

答案有点出入...

nkrealman

ultikiller

答案有点出入...
Allmaths 发表于 11-10-2010 08:05 PM

请问下

- 除能在中间？能做到分子分母各自除的功效？求运作排式。

- cos y / cos y 有什么确切推算出的理由？虽然我知道只要把答案反向推算就能找到，不过我觉得好像有什么最佳理由。

Allmaths

请问下

- 除能在中间？能做到分子分母各自除的功效？求运作排式。

- cos y / cos y 有什么 ...
ultikiller 发表于 11-10-2010 10:05 PM

peaceboy

请问下

- 除能在中间？能做到分子分母各自除的功效？求运作排式。

- cos y / cos y 有什么 ...
ultikiller 发表于 11-10-2010 10:05 PM

[p cos y　－sin y ]/[cos y-p sin y] <<<<to get rid of [cos y] and make the [sin y] become [tan y] , we know that we must divide it by [cos y]
the same thing also to make the [cos y-p sin y] to [1-p tan y]
so we divide both the upper part and lower part by [cos y] which is equal to divide [cos y / cos y] or 1 to finish ur "show"
中文．．．

ultikiller

Allmaths 发表于 11-10-2010 10:27 PM

发现了个错误。
答案是tan x =  p - tan y/1 - p tan y

你的答案则是是  tan x = p - tan y/1 + p tan y

Allmaths

发现了个错误。
答案是tan x =  p - tan y/1 - p tan y

你的答案则是是  tan x = p - tan y/1 + p ...
ultikiller 发表于 11-10-2010 10:41 PM

   所以之前我说我的答案有点出入...

ultikiller

所以之前我说我的答案有点出入...
Allmaths 发表于 11-10-2010 10:43 PM

呵呵。怎么那么难解啊？

Allmaths

呵呵。怎么那么难解啊？
ultikiller 发表于 11-10-2010 11:10 PM

   
有两个可能:
1)我做错


2)题目错