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Mathematics: Post your doubts here!

Dug

Dug

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suhaib05 said:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s09_qp_3.pdf

Q10(ii) and (iii). Can someone provide full working out? I would really appreciate it because I'm stuck :/
Click to expand...
ii)
A = ⌡x² √(1 - x²) dx

x = sinΘ
dx = cosΘ dΘ

A = ⌡sin²Θ √(1 - sin²Θ) cosΘ dΘ
A = ⌡sin²Θ cos²Θ dΘ
A = ⌡(sinΘ cosΘ)(sinΘ cosΘ) dΘ
A = ⌡(½ sin2Θ)(½ sin2Θ) dΘ
A = ¼ ⌡sin² 2Θ dΘ

The curve touches the x-axis at 0 and 1.

Limits:
x = 0, Θ = 0
x = 1, Θ = π/2

iii)
A = 1/4 ⌡sin² 2Θ dΘ

cos 2Θ = 1 - 2sin² Θ
cos 4Θ = 1 - 2sin² 2Θ
sin² 2Θ = (1 - cos 4Θ)/2

A = ¼ ⌡(1 - cos 4Θ)/2 dΘ
A = 1/8 ⌡(1 - cos 4Θ) dΘ
A = 1/8 (Θ + ¼ sin 4Θ)

Insert limits:
A = 1/8 (π/2) = π/16
 
P

PhyZac

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prekshya said:
s-03-qp-6 ques no 3 ii help plz
Click to expand...
103-115/sd = z [sd=standard deviation, ]
-12/sd = -z
Capture.PNG
u see, the red area wanted, is identical to the area below the green.
therefore.
12/sd = z (with no negative sign)
the probablity of z is 80% (0.80)
from the table u find that z is 0.842

thus (-z) = -0.842
therefore -12/sd = -0.842
sd = 14.3
 
syed1995

syed1995

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littlecloud11 said:
Phy, chem, Bio, Math and English.
Not really. I applied for Imperial, so I thought having it might give me an edge and I like math so couldn't hurt.
Click to expand...

Damn.. and here I thought my combination was difficult..

Further Maths, Bio, Chem, Physics, English.. one's mind would totally explode.. unless of course it's littlecloud11's mind :p
 
iKhaled

iKhaled

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ZainH said:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_w12_qp_42.pdf

Q3.

Explanation as well please x)
Click to expand...
okay the way i did this question is i used two equations then i used simultaneous equations

the equations i thought of and guessed they would help me are v = u +at and s = ut+1/2at^2....lets apply these equations to the motion through AB and BC

AB: V = u+at which is V= u+5a we also have 55= 5u + 12.5a

now lets take calculations for the motion from B to C....

BC: V2 = U2+5a and 65= 5U2+12.5a....now if u notice that U2 will be equal to V from because the final velocity of AB is the initial velocity of BC so U2= V(from the above equation)

65= 5(u+5a) +12.5a which is 65= 5u+37.5a...now u have two equations:

1. 55= 5u + 12.5a
2. 65= 5u+37.5a

use simultaneous equations and u will get a = 0.4 and u is 10...i hope u did get it now!
 
syed1995

syed1995

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A star said:
a friend of mine has physics chem further maths accel maths accounts and eco in A2
Click to expand...

Tell him.. he's crazy.. what field is he after? That combination would get him pretty much into anything except Medical.

imo. Pure sciences + Maths is the toughest combo..
 
A

A star

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syed1995 said:
Tell him.. he's crazy.. what field is he after? That combination would get him pretty much into anything except Medical.

imo. Pure sciences + Maths is the toughest combo..
Click to expand...
i dont know what he wants he took 14 or 15 subs in O levels and is on full exceptional scholarship. asked him the same thing he said opens up possibilities well eco is a choice since he is still in As :confused:
 
ZainH

ZainH

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iKhaled said:
okay the way i did this question is i used two equations then i used simultaneous equations

the equations i thought of and guessed they would help me are v = u +at and s = ut+1/2at^2....lets apply these equations to the motion through AB and BC

AB: V = u+at which is V= u+5a we also have 55= 5u + 12.5a

now lets take calculations for the motion from B to C....

BC: V2 = U2+5a and 65= 5U2+12.5a....now if u notice that U2 will be equal to V from because the final velocity of AB is the initial velocity of BC so U2= V(from the above equation)

65= 5(u+5a) +12.5a which is 65= 5u+37.5a...now u have two equations:

1. 55= 5u + 12.5a
2. 65= 5u+37.5a

use simultaneous equations and u will get a = 0.4 and u is 10...i hope u did get it now!
Click to expand...

Oh wow thanks a ton , that helped :D
 
syed1995

syed1995

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A star said:
i dont know what he wants he took 14 or 15 subs in O levels and is on full exceptional scholarship. asked him the same thing he said opens up possibilities well eco is a choice since he is still in As :confused:
Click to expand...

Ah I see.. he's one of those.. Well I had only 8 subjects in O Levels. And I was happy with that! imo having too many subjects disrupts one's concentration.. If one's mind is focused that Yes I want to do engineering or Medical.. and he takes all relevant subjects.. then it makes sense..

But if one takes subject combination like Accounts, Biology, Chemistry, Computer, Sociology & Law or something similar.. I'd say the person's mind isn't set on what he wants to do in the future...
 
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