Mathematics: Post your doubts here!

[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?

 

[PANDA-]

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)

To be honest... I find vectors one of the easier topics. Functions is pretty hard..

 

[Mohsin41]

I have almost done with 10 past papers and still on 60,62/75 in P1.... grade thresholds are to high. I am worried for the final

 

[iKhaled]

To be honest... I find vectors one of the easier topics. Functions is pretty hard..

functions suck

 

[Mohsin41]

specially the functions integrated with trigonometry or the functions question which is Q10 or 11......

 

[PANDA-]

specially the functions integrated with trigonometry or the functions question which is Q10 or 11......

Yes that's especially hard. Imagine if no functions question comes in our exam, awesome.

 

[Sanis]

I have a problem in the whole vector chapter for p3 .. does anybodyhave a link for notes I can use to understand a2 vectors? thanks

 

[Mohsin41]

I have a problem in the whole vector chapter for p3 .. does anybodyhave a link for notes I can use to understand a2 vectors? thanks

If you want to have best understanding than read Pure Mathematics 2&3 OF (Hodder Education)

 

[Muhammad Muneeb]

http://papers.xtremepapers.com/CIE/...S Level/Mathematics (9709)/9709_w11_qp_12.pdf
q3 (ii)
and thanks for the help previously

 

[Alice123]

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

its the same thing

 

[Muhammad Muneeb]

http://papers.xtremepapers.com/CIE/...S Level/Mathematics (9709)/9709_w11_qp_12.pdf
q9 (i), how do i calculate co ordiates of D :/

 

[PANDA-]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_w11_qp_12.pdf
q3 (ii)
and thanks for the help previously

AB = OB - OA
AB = (2-5)i+(7-1)j+(p-2)k
= -3i + 6j + 2k

Now make it a unit vector, so we can later multiply the magnitude of the vector we need (28) to get the vector itself.
For that you'll need to find the modulus by finding the square root of the sum of i^2, j^2 and k^2...

That gives you
Modulus = sqrt((-3)^2 + 6^2 + 2^2)
= 7

To find the unit vector, we need to divide our vector by the modulus, or multiply it by 1/modulus as so...

Unit vector = 1/7(-3i+6j+2k)

Multiply the magnitude (28) by the unit vector, you'll get
(1/7)(28)(-3i+6j+2k)

4(-3i+6j+2k)
Ans. = -12i+24j+8k