Mathematics: Post your doubts here!

[applepie1996]

Check the first link again. There is no part 4...

w05 qp 3
Q7 iii

Mark a point at (1, 2).
|z| = |z - 1 - 2i|
|z - (0 + 0i)| = |z - (1 + 2i)|
Construct a perpendicular bisector of (0, 0) and (1, 2).
----------------------------
w04 qp 3
Q9 iii

Put Q in m:
<2, 0, -1> = <-2, 2, 1> +t<-2, 1, 1>
From one equation, you get t = -2. Test the remaining two equations with this value. It should satisfy them.

PQ = <-2, -1, -3> (By putting s = 2)
Make a dot product with 'm' and see if the answer is zero.
-----------------------
w04 qp 3
Q10
i)
V = 1000h
dV/dh = 1000

dV/dt = 30 - k√h

dh/dt = dh/dV x dV/dt
dh/dt = (1/1000) (30 - k√h)

When h = 1, dh/dt = 0.02
0.02 = (1/1000) (30 - k)
k = 10

dh/dt = 0.01(3 - √h)

ii)
[(x - 3)/x] dx = 0.005 dt
(1 - 3/x) dx = 0.005 dt
x - 3ln|x| = 0.005t + c

When x = 3, t = 0
3 - 3ln3 = c

x - 3ln|x| = 0.005t + 3 - 3ln3
0.005t = x - 3 - 3ln|x| + 3ln3
t = 200(x - 3 + 3ln|3/x|)

iii)
x = 3 - √h
x = 3 - √4 = 1

t = 200(1 - 3 + 3ln|3/1|) = 259

thank you very very very much
i get it now
oh yeah sorry
i meant part 2

 

[mania _ manal]

Can some1 help me with octnov 2010 pp41 question 6 lst part

 

[sma786]

See, they said that P(X > 5.2) = 0.9
-Φ(z) = 0.9
z = 1.282 [so from the Normal distribution table]
-z= -1.282
Very simplified, if u dont get ask.

Thanku, i got it
can you send me a link of the normal dis. table please??

 

[PhyZac]

Thanku, i got it
can you send me a link of the normal dis. table please??

You see, this is the syllabus.
Go to page 31, you will find the formula booklet, now next few pages is the table.
http://papers.xtremepapers.com/CIE/...d AS Level/Mathematics (9709)/9709_y13_sy.pdf

 

[sma786]

You see, this is the syllabus.
Go to page 31, you will find the formula booklet, now next few pages is the table.
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_y13_sy.pdf

Thanks, you're an angel (^_^)

 

[sma786]

http://papers.xtremepapers.com/CIE/...AS Level/Mathematics (9709)/9709_s07_qp_6.pdf
In question 6 (ii)
Why does the markscheme show 1-(7.5-8) and also (8/7.5) when the P to find is just 7 ?
Markscheme : http://papers.xtremepapers.com/CIE/...AS Level/Mathematics (9709)/9709_s07_ms_6.pdf

 

[PhyZac]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s07_qp_6.pdf
In question 6 (ii)
Why does the markscheme show 1-(7.5-8) and also (8/7.5) when the P to find is just 7 ?
Markscheme : http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s07_ms_6.pdf

This is because this is an approximation, not normal.

So you add 0.5 or subtract 0.5 depending on the question. Since this is more than, you take 7.5

EDIT: Whenever you approximate, make sure to make continuity correction.

 

[cool Asviva]

http://papers.xtremepapers.com/CIE/...AS Level/Mathematics (9709)/9709_w06_qp_6.pdf

question 6 part ii. please explain how 7p3 not 6p3?

 

[PhyZac]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_w06_qp_6.pdf

question 6 part ii. please explain how 7p3 not 6p3?

Solved this before. Here you go.

6 men 3 women
no women beside each other
thus
_M_M_M_M_M_M_
u see, i made blanks between men, and women can choose any of these blanks.
therefore
6! x 7P3 ( 6! because u rearrange the 6 men) (7P3, because out of these 7 blanks, 3 are permutated depeneding on where will 3 women stay)
answer = 151200

 

[cool Asviva]

Solved this before. Here you go.

6 men 3 women
no women beside each other
thus
_M_M_M_M_M_M_
u see, i made blanks between men, and women can choose any of these blanks.
therefore
6! x 7P3 ( 6! because u rearrange the 6 men) (7P3, because out of these 7 blanks, 3 are permutated depeneding on where will 3 women stay)
answer = 151200

the question is no two women together...i thought three can be together...!

 

[Dudu]

You could try the trigonometry notes linked on the first page of this thread.
Here's what my guide says about the ques:

a: indicates the amplitude of the curve which is the max or min range of the curve from the mean position.
so, a=9-3=6

b: indicates the periodicity of the curve. we see that in the given figure there are two main cycles in a normal period of sine.
therefore, b=2

c: indicates the vertical shift in the graph from the horizontal axis, which in this case is 3 units.
thence, c=3 units

Cheers

 

[sma786]

Formula for Variance in Expectation and variance?!

 

[shezi1995]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s10_qp_43.pdf

#7 (ii) and (iii) urgently please

ii) First you have to realise that boxes do not have to slide. We know the mass of A which is 200 kg and can calculate the vertical contact force which is equal to weight i.e 2000 N. Multiply the C. of friction i.e 2000*0.2 to get 400 N. It means that this is maximum force which the box B applies on box A to keep it going without sliding. So using F=ma , we get max a i.e. a=400/200=2 ms^-2.
iii)because you have the max a then you can use again F=ma to calculate the maximum resultant force on A as acceleration will be same for the boxes. resultant force=(200+250)*2=900. resultant=P-3150 .So P=3150 + 900 to get 4050.
I hope you have understood it.

 

[Amaryllis]

can anyone please explain Q9 part i http://papers.xtremepapers.com/CIE/...S Level/Mathematics (9709)/9709_s11_qp_12.pdf

how can i get the domain and range from an equation? i usually face problem in these parts

 

[shezi1995]

can anyone please explain Q9 part i http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s11_qp_12.pdf

how can i get the domain and range from an equation? i usually face problem in these parts

in trigonometric equations, you should always use the range of sin, cos, and tan. in this one, f(x)=3-4cos^2(x) , you know that -1=<cos<=1. So 0=<cos^2<=1 as -1 becomes 1. Since we have negative 4cos^2, we reverse the signs and multiply by 4 to get 0=>-4cos^2>=(-4). Then simply add 3 to the inequality to get -1=<3-4cos^2(x)<=3. So your range is -1=<f<=3.

 

[syed1995]

the question is no two women together...i thought three can be together...!

If you put three women together.. 2 will get together..

it will be WWW .. WWM both mean that 2 women are together .. regardless of who is next to them.

 

[Amaryllis]

in trigonometric equations, you should always use the range of sin, cos, and tan. in this one, f(x)=3-4cos^2(x) , you know that -1=<cos<=1. So 0=<cos^2<=1 as -1 becomes 1. Since we have negative 4cos^2, we reverse the signs and multiply by 4 to get 0=>-4cos^2>=(-4). Then simply add 3 to the inequality to get -1=<3-4cos^2(x)<=3. So your range is -1=<f<=3.

thank you so much, can you explain how to get domain and range for ex. in q 11ii http://papers.xtremepapers.com/CIE/...AS Level/Mathematics (9709)/9709_w07_qp_1.pdf

 

[Rutzaba]

wish u cud have been there wen i was giving my s2... there was no one at awlll to help :/ PhyZac

 

[Rutzaba]

and im srry fr tagging ... u must be busy... sorry...

 

[PhyZac]

thank you so much, can you explain how to get domain and range for ex. in q 11ii http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_w07_qp_1.pdf

Well from one you got
2(x-2)^2 + 3

now you have to know the possible values of y.

The x values are all real numbers ( as stated in the question)

Now what i did was, make the red bit of the equation zero , to do this, you have to make x as 2, now 2(2-2)^2 + 3 will equal 3, then i try a negative number, i choose -1, 21 came, so this bigger than 3, i tried a positive number as 1, and 5 came, so in all cases, a number bigger than three comes, so
y => 3, [i mean y is more than or equal to 3]