Mathematics: Post your doubts here!

[anishh]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_w09_qp_42.pdf.plz solve no7(ii)

 

[aleezay]

URGENT HELP NEEDED:
this Q isnt directly from Alevel math but it might brush up the skills of all the mathematicians out there. So PLEASE give it a try:

A person is trapped in a dark cave with 3 ways out. One of them leads to safety after 2hrs of travel while the other 2 would return him to the cave after 3 and 5hrs of travel respectively. Assuming that the person is equally likely to opt for any of the openings at all times, what is the expected length of time he spends travelling until reaching safety?

 

[aleezay]

UrGENT HELP in this one too:

Consider an m * n array of lattice points (points with integer coordinates) on a plane. Determine the no of
a) axis-parallel squares (whose sides are parallel to on of the axis)
b) axis-parallel rectangles
c) squares (not necessarily axis parallel)
d) rectangles (")
e) Triangles
whose vertices are in m*n array and have positive area.
PLEASE be kind enough to solve these before 7a.m tomorrow. Id be highly grateful

 

[Just visiting]

I need help in how to differentiate sin^3 (X)
The answer is 3sin^2(2X)
Thanks in advance

 

[Alice123]

Can any1 help me with permutations n combinations? i badly need help

 

[abcde]

URGENT HELP NEEDED:
this Q isnt directly from Alevel math but it might brush up the skills of all the mathematicians out there. So PLEASE give it a try:

A person is trapped in a dark cave with 3 ways out. One of them leads to safety after 2hrs of travel while the other 2 would return him to the cave after 3 and 5hrs of travel respectively. Assuming that the person is equally likely to opt for any of the openings at all times, what is the expected length of time he spends travelling until reaching safety?

Firstly, I apologise for the late reply. :/ You may not need this anymore, but this question is really interesting!

Lets say E is the expected time of reaching safety.
=> E = (1/3).2 + (1/3).(3+E) + (1/3).(5+E) (probability of 1st pick + probability of 2nd pick + probability of 3rd pick. E is added in 2nd and 3rd pick cuz the person is in the exact same scenario after travelling those 3 and 5 hours, respectively.)
=> E = [2+ (3+ E) + (5 + E)]/3
=> 3E = 2E + 10
=> E = 10.

So, it would take the person 10 hours (estimated).

 

[19islandprincess96]

In Stats 1 year 2012 q 4, how are we supposed to find the median and interquartile range? Do we do it by writing them all down or is there a specific method of doing it?
Here's the paper I am talking about: http://papers.xtremepapers.com/CIE/...S Level/Mathematics (9709)/9709_s12_qp_62.pdf

 

[Yousif Mukkhtar]

Guys need some help here:
http://papers.xtremepapers.com/CIE/...S Level/Mathematics (9709)/9709_w11_qp_62.pdf
q3) b) How did it come to
7!/3!x6?

 

[falcon678]

salam!
can anyone help me with how to differentiate and integrate expresion involvin brakets e.g (3x^2+2x)^3
thanks!

 

[whitecorp]

salam!
can anyone help me with how to differentiate and integrate expresion involvin brakets e.g (3x^2+2x)^3
thanks!

You would have to employ the chain rule of differentiation.

Generally speaking, if you are asked to differentiate [ f(x) ]^n wrt x,
then the derivative is given by n* [ f(x) ]^(n-1) * f '(x)

If we consider your example (3x^2+2x)^3, then f(x)= 3x^2+2x , n=3 and f '(x)= 6x +2,
which therefore gives us the overall derivative as 3*(3x^2+2x)^2 * (6x+2) (shown)

Hope this helps. Peace.

 

[whitecorp]

In Stats 1 year 2012 q 4, how are we supposed to find the median and interquartile range? Do we do it by writing them all down or is there a specific method of doing it?
Here's the paper I am talking about: http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s12_qp_62.pdf

I believe listing them out in a systematic fashion is the only way to go. Peace.

 

[whitecorp]

I need help in how to differentiate sin^3 (X)
The answer is 3sin^2(2X)
Thanks in advance

Do you mean sin(X) raised to the power of 3? Because if that is the case, the answer you provided is incorrect.

d/dx [ sin^3 (X)]
= d/dx [ sin (X) ] ^3

= 3 [ sin (X) ] ^2 * cos(X) (shown)

For your answer provided, 3sin^2(2X) = 3[ sin(2X) ] ^2
= 3 [ 2 sin(X) cos(X)] ^2

= 12 sin ^2 (X) cos ^2 (X)

This clearly isn't the same as 3 [ sin (X) ] ^2 * cos(X) .

Hope it helps. Peace.

 

[magnesium]

http://papers.xtremepapers.com/CIE/...AS Level/Mathematics (9709)/9709_s08_qp_3.pdf
Q9 b HELP!!!!!!!!!!!!!!

 

[sma786]

Mj 2007. Paper 01..
Question 3.. Prove the identity
...
Help plzz

 

[magnesium]

http://papers.xtremepapers.com/CIE/...AS Level/Mathematics (9709)/9709_w08_qp_3.pdf
Q10..................... PLZ HELP!!!!!!!!!!!!!!!!!!!

 

[ZainH]

Pretty simple question from mechanics.
A lift bringing miners to the surface of a mine shaft is moving with an acceleration of 1.2 m.s-2 . The total mass of the cage and the miners is 1600kg. Find the tension in the cable.

For some reason I'm getting 17920, where as the answer is 17900. Ugh, help please .___.

 

[~`Heba`~ :)]

Mechanics question!
A car of mass 1000 kg moves along a horizontal straight road with its engine working at a contant rate of 25 KW. Assuming the work done by the car's engine is equal to kinetic energy generated, find the time taken to reach a speed of 30m/s.
The actual time taken is 31.6s and the car travels a distance of 680m in this time. Assuming there's an air resistance of magnitude R newtons,
(I) find the value of R.
(ii) the acceleration of the car when it's speed reaches 30m/s.
Please help thanks

 

[~`Heba`~ :)]

Pretty simple question from mechanics.
A lift bringing miners to the surface of a mine shaft is moving with an acceleration of 1.2 m.s-2 . The total mass of the cage and the miners is 1600kg. Find the tension in the cable.

For some reason I'm getting 17920, where as the answer is 17900. Ugh, help please .___.

I got 17920 too :/ , maybe the answer is corrected to the nearest 100th

 

[ZainH]

I got 17920 too :/ , maybe the answer is corrected to the nearest 100th

Sounds about right, or the book could always be wrong.
Thanks for your help x)

 

[ayeshaK]

hi can anyone here tell me any good books for pure mathematics except for the cambridge one because its not that good