Mathematics: Post your doubts here!

[PhyZac]

owww......yes i do
but i find it a lil' difficult to apply it
:/

I will tell the easy which i think your book states it.

See, i did a sketch.

For i as I said cover the first row and do that multipliction then subtract.

For j do same thing but cover second row , and whatever value comes take its negative form (if +ve then -ve if -ve then +ve)

For k cover third row.

 

[iKhaled]

Pure Mathematics 2 and 3 by Hugh Neil and Doughlas Quadling.

open page 182 and check 13.4 the common perpendicular thingy because you need to know it so i can explain the third part..tell me if u had any doubts about that part ok ?

 

[iKhaled]

I will tell the easy which i think your book states it.

See, i did a sketch.

For i as I said cover the first row and do that multipliction then subtract.

For j do same thing but cover second row , and whatever value comes take its negative form (if +ve then -ve if -ve then +ve)

For k cover third row.

i think it would be better for him if he checked it from the book..isn't that better ?

 

[PhyZac]

i think it would be better for him if he checked it from the book..isn't that better ?

Yes ofcourse! I learned it from that book only.

Plus, when you learn it Soldier313, before solving that past paper question, I would recommend you to try some cross product question to make sure that chapter sticks to your head!

 

[Soldier313]

PhyZac iKhaled
JazakAllah khair bros!
Thanx a ton......
i got the concept alhamdulillah, if i do have more doubts will let you guys know......

 

[iKhaled]

PhyZac iKhaled
JazakAllah khair bros!
Thanx a ton......
i got the concept alhamdulillah, if i do have more doubts will let you guys know......

anytime bro

 

[abruzzi]

http://papers.xtremepapers.com/CIE/...AS Level/Mathematics (9709)/9709_s06_qp_1.pdf
I need help with question 8 (i & ii).. I'm unable to find the unit vectors OD and OB. Someone please explain that.
Thanks

 

[PANDA-]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s06_qp_1.pdf
I need help with question 8 (i & ii).. I'm unable to find the unit vectors OD and OB. Someone please explain that.
Thanks

OD = 4i+4j+5k

Now why? Well, start with 4i, this is because the length OA is 14m, and DE is 6, you need to subtract 6 from 14 and then divide by two, as this is how you'll get the length of i... Think about it, because I don't know how else to explain it . 4j because it goes halfway through the 8m, as the opposite side of the base rectangle are equal, so 8/2 = 4... so 4j. 5k is easy because they said the roof is at a height of 5cm, and k is the movement on the y axis, so 5k... 4i+4j+5k.

OB is much easier..
OB = 14i + 8j

14i because it moves 14m along from O to A, and then 8j because it moves 8m from A to B.

Now to find the angle...

a.b=|a||b|cosθ

4(14)+4(8) = √(4^2 + 4^2 + 5^2)√(14^2 + 8^2)cosθ
88 = √57 √260 cosθ
88=121.7cosθ
cosθ = 88/121.7
θ = cos^-1(88/121.7)
θ=43.7

... Yup correct

 

[peter brown]

ii) Probability of length less than 73 m and length greater than 77 m is the same since they are the same distance from mean. A normal distribution curve is symmetric about its mean.
P(X<73) = P(X>77) = 0.15

Let X represent the number of rolls having length greater than 77 m.
n = 8
p = 0.15
q = 0.85

P(X<3) = P(X = 0) + P(X = 1) + P(X = 2)
P(X<3) = (8C0) (0.85)^8 + (8C1) (0.15)(0.85)^7 + (8C2) (0.15)²(0.85)^6
P(X<3) = 0.895

thanks alot Dug. May God bless you. sorry for late reply

 

[syed1995]

http://papers.xtremepapers.com/CIE/...S Level/Mathematics (9709)/9709_w12_qp_11.pdf

Question No. 11 part i..

Just do the differentiation for me.. and find dy/dx=0 I am getting gradient as -1/3 .. while the MS states the gradient is 1/3 :\

 

[iKhaled]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_w12_qp_11.pdf

Question No. 11 part i..

Just do the differentiation for me.. and find dy/dx=0 I am getting gradient as -1/3 .. while the MS states the gradient is 1/3 :\

dy/dx is 2(6x+2)^-2/3 is that what u got ?

 

[abruzzi]

OD = 4i+4j+5k

Now why? Well, start with 4i, this is because the length OA is 14m, and DE is 6, you need to subtract 6 from 14 and then divide by two, as this is how you'll get the length of i... Think about it, because I don't know how else to explain it . 4j because it goes halfway through the 8m, as the opposite side of the base rectangle are equal, so 8/2 = 4... so 4j. 5k is easy because they said the roof is at a height of 5cm, and k is the movement on the y axis, so 5k... 4i+4j+5k.

OB is much easier..
OB = 14i + 8j

14i because it moves 14m along from O to A, and then 8j because it moves 8m from A to B.

Now to find the angle...

a.b=|a||b|cosθ

4(14)+4(8) = √(4^2 + 4^2 + 5^2)√(14^2 + 8^2)cosθ
88 = √57 √260 cosθ
88=121.7cosθ
cosθ = 88/121.7
θ = cos^-1(88/121.7)
θ=43.7

... Yup correct

Hmm I didnt understand how you found the unit vector OD. Isn't the length of i just OA = 14?
I'll really appreciate if you could explain that to me from the diagram, that is, if you're free and don't mind to do so
The rest is all clear..

 

[PANDA-]

Hmm I didnt understand how you found the unit vector OD. Isn't the length of i just OA = 14?
I'll really appreciate if you could explain that to me from the diagram, that is, if you're free and don't mind to do so
The rest is all clear..

They didn't ask for the unit vector, they just asked for the vector and its magnitude, I guess I forgot to mention the magnitude...
Well the magnitude is the square root of the sum of i^2, j ^2, k^2. Which is √(i^2+j^2+k^2).
Which is √(4^2 + 4^2 + 5^2) = √57.

Unit vector would be another story, where you divide the vector itself by the magnitude.

 

[syed1995]

dy/dx is 2(6x+2)^-2/3 is that what u got ?

naw.. that's incorrect.

the dy/dx would be 2(6x+2)^-4/3

-1/3 -1 = -4/3 not -2/3 .. and there was a calculation error on my part.. the m is 1/2.

 

[syed1995]

They didn't ask for the unit vector, they just asked for the vector and its magnitude, I guess I forgot to mention the magnitude...
Well the magnitude is the square root of the sum of i^2, j ^2, k^2. Which is √(i^2+j^2+k^2).
Which is √(4^2 + 4^2 + 5^2) = √57.

Unit vector would be another story, where you divide the vector itself by the magnitude.

Vectors can be challenging sometimes... But still.. vectors in P1 are lots easier than the vectors which I did in O level Add Maths (Which I still haven't understood)

 

[ahmed abdulla]

is it (x^2-3)/2????

its 1 / 2*(x^2-3)

 

[aroojshahzad]

is my scientific calculator casio fx-570ES allowed for the AS examination?

 

[Manobilly]

is my scientific calculator casio fx-570ES allowed for the AS examination?

You can use any type of calculator unless it is:
a graphical calculator
a programmable one
a one with with a qwerty keyboard( ie ones which look like, or function like computers)
ones with the ability to communicate with other devices etc

 

[iKhaled]

naw.. that's incorrect.

the dy/dx would be 2(6x+2)^-4/3

-1/3 -1 = -4/3 not -2/3 .. and there was a calculation error on my part.. the m is 1/2.

excuse me? why -1/3-1 and not 1/3-1

 

[iKhaled]

naw.. that's incorrect.

the dy/dx would be 2(6x+2)^-4/3

-1/3 -1 = -4/3 not -2/3 .. and there was a calculation error on my part.. the m is 1/2.

yes using the equation i posted above will give u a gradient of 1/2 so how come u say its wrong?