Mathematics: Post your doubts here!

[A star]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s10_qp_12.pdf
Please help me with qn no. 11 (ii & iii).

I've tried to sketch the graph (Attachment)... please check if its correct. For (iii), I'm totally confused!

Thanks

dude the curve you have drawn is completely wrong for one thing its axis is y=4 and amplitude is clearly 3 . hence redraw the curve and get the correct answer

 

[tanmaydube]

sagar65265 thanks a lot!!!!

 

[tanmaydube]

part (ii) PLEASE

Thank You!

 

[Farhan Chowdhury]

5 The weights of letters posted by a certain business are normally distributed with mean 20 g. It is
found that the weights of 94% of the letters are within 12 g of the mean.
(i) Find the standard deviation of the weights of the letters. [3]

Could someone please answer this and show ALL the steps? Thank you

 

[Dug]

View attachment 23574

part (ii) PLEASE

Thank You!

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

 

[Silent Hunter]

http://papers.xtremepapers.com/CIE/...S Level/Mathematics (9709)/9709_s12_qp_31.pdf

need help in Q10 first part

thank you

 

[tanmaydube]

Dug thanks a lot!

 

[Dug]

5 The weights of letters posted by a certain business are normally distributed with mean 20 g. It is
found that the weights of 94% of the letters are within 12 g of the mean.
(i) Find the standard deviation of the weights of the letters. [3]

Could someone please answer this and show ALL the steps? Thank you

__8(µ-12)____20(µ)____32(µ+12)__

P(8 > X > 32) = 0.94
P(X < 8) = P(X > 32) = 0.03

P(Z < -12/σ) = 0.03
1 - φ(12/σ) = 0.03
φ(12/σ) = 0.97
12/σ = 1.881
σ = 6.38

 

[applepie1996]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s12_qp_31.pdf

need help in Q10 first part

thank you

okay so here goes

so the equation is 2 tan2x + 5 tan^2 x = 0 --------- (1)
you open up tan2x = 2tanx/1-tan^2 x
now substitute this in the equation numbered (1) and you get .......
2 ( 2tanx/1-tan^2 x ) + 5 tan^2 x = 0-----------(2)
now since the question says use tanx as "t" substitute tanx as t in equation (2)
so you get , 2( 2t / 1- t^2 ) + 5 t^2 = 0
then open up the bracket and remove the fraction by multiplying the whole equation with 1-t^2 you get........
4t + 5t^2 - 5t^4 = 0
take "t" as a common factor and you get .........
t(4 + 5t - 5t^3) = 0
so t=0 and 4 + 5t - 5t^3=0-----------3
rearrange equation 3 as 5t^3=4+5t then divide equation by 5 ............you get
t^3=0.8+t and then cube root the other side
and wallah.............you get the answer

 

[Alice123]

http://papers.xtremepapers.com/CIE/...AS Level/Mathematics (9709)/9709_s08_qp_3.pdf
sum1 help with Q9ii.... Dug syed1995

 

[immie.rose]

can anyone help me by telling me how to find out angle between tangents and angle between tangents and x axis :/. for some reason i keep forgetting

You need to find the gradients of both the tangents, and then use the formula: tan-1[m2-m1/1-(m2*m1)]
(where m2 and m1 are the gradients, and m2 is the bigger grad.)

 

[applepie1996]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s08_qp_3.pdf
sum1 help with Q9ii.... Dug syed1995

okay so i will try to do it

 

[applepie1996]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s08_qp_3.pdf
sum1 help with Q9ii.... Dug syed1995

ok so you i am assuming you know that to find the integration of the volume you multiply the equation with pi and square it
so you get (pi) [(e^(-1/2)x)(sqrt(1+2x))^2 then you get pi e^-x (1+2x)
after you get that equation
you integrate it
so integartion of pi e^-x (1+2x) gives
oh and make sure you integrate by parts as there is no other way

 

[syed1995]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s08_qp_3.pdf
sum1 help with Q9ii.... Dug syed1995

Don't have P3.

 

[Farhan Chowdhury]

__8(µ-12)____20(µ)____32(µ+12)__

P(8 > X > 32) = 0.94
P(X < 8) = P(X > 32) = 0.03

P(Z < -12/σ) = 0.03
1 - φ(12/σ) = 0.03
φ(12/σ) = 0.97
12/σ = 1.881
σ = 6.38

THANK YOU SO MUCH!!
could you please explain why P(X < 8) = P(X > 32) = 0.03?

 

[Rutzaba]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s08_qp_3.pdf
sum1 help with Q9ii.... Dug syed1995

http://i1275.photobucket.com/albums/y444/Rutzaba/mind_zpsa77f0ef6.png

 

[tompapaya]

questions about pure math 1
i do not have any ideas about this kinds of questions.
could u give me some help? thanks a lot!

 

[tompapaya]

QUESTION abt statistics!
how abt the question 3?
HELP!pls!

 

[salvatore]

dude the curve you have drawn is completely wrong for one thing its axis is y=4 and amplitude is clearly 3 . hence redraw the curve and get the correct answer

Yeah.. I figured it out. Thanks

 

[Rutzaba]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s08_qp_3.pdf
sum1 help with Q9ii.... Dug syed1995

did u get it? or u just liked it?