Mathematics: Post your doubts here!

[reina81]

e^x = 1 + 6e^−x
Using u = e^x
The equation becomes
u = 1 + 6/u
u^2 = u + 6
u^2 - u - 6 = 0
(u+2)(u-3) = 0
u = -2 or u = 3
e^x = -2
This cannot be solved as ln or lg of a negative number is undefined!

The only solution is
e^x = 3
x = ln3 / lne
x = ln3
x = 1.10

We take lne^x
but according to power rule, the power becomes coefficient
so lne^x = xlne
and lne = 1
so
xlne = x

See the notes i posted on logs above !

But why didnt we take lne^3 as well?

 

[smzimran]

smzimran Assalamoalaikum wr wb!

I need help with the last part of the last question of Nov:2011 # 3

mark scheme

I do know how to do it...but i cant seem to get the answer...!

it's like we take the root of − 2 ± 2 root 3i

how i do is...equate that to (a + bi)^2 but..if we simplify...i get a^2 + b^2 = -2.....and this cant be solved...ms uses a^2 - b^2.....can u tell me when exactly do we use '-' b^2 ?

 

[smzimran]

But why didnt we take lne^3 as well?

Why would we ?

 

[smzimran]

hey could you please help me with my doubt.I've posted it twice here but haven't gotten any reply.Since you've been helping a lot of people,I am asking you.
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_w11_ms_32.pdf
On a sketch of an Argand diagram, shade the region whose points represent the complex numbers z which satisfy the inequality |z − 3i | ≤ 2. Find the greatest value of arg z for points in this region.
The question asks about greatest value of argument,sadly I don't even know the least argument value so could you just explain it to me or better if you are of any links,will u let me know?
Please do reply soon.thanks

p.m me your email adress i will 4rward you the notes on least and greatest values of arguments and all

 

[Mahnoor Khanm]

Hey Guys how is ur math p3 prep? i suck at vectors. Any tips? and anyone from lgs here?

 

[reina81]

Why would we ?

ok so does this mean that any time we have a question like this, you know the last part, and i have to take ln of both sides, i simply add it to whatever constant they've given? what if its an equation like 2x or something?

 

[RGBM211]

http://www.xtremepapers.com/papers/...S Level/Mathematics (9709)/9709_s11_qp_31.pdf
http://www.xtremepapers.com/papers/...S Level/Mathematics (9709)/9709_s11_ms_31.pdf

question no.8 how to show the arguement u is PIE/2 i knw its pie by 2 since i got u=-3i but how to show should i draw a graph or i should just say that the cordinates (0,-3i) lies on the y axis thus the angle made with the x axis is -pie/2
Anyone :?

 

[RGBM211]

some please reply to my previous posts as well

 

[smzimran]

ok so does this mean that any time we have a question like this, you know the last part, and i have to take ln of both sides, i simply add it to whatever constant they've given? what if its an equation like 2x or something?

Plz read my notes on logs above

 

[smzimran]

some please reply to my previous posts as well

Yaar im a little tired for now, will solve it in the afternoon!

 

[user]

View attachment 9599

what a silly mistake...when taking square of bi i totally forgot i

jazakAllah khairen!!

 

[user]

p.m me your email adress i will 4rward you the notes on least and greatest values of arguments and all

2pac
check the first post of this thread there are some links to notes for that..

 

[user]

Hey Guys how is ur math p3 prep? i suck at vectors. Any tips? and anyone from lgs here?

assalamoalaikum wr wb!

some notes

Check this: http://www.xtremepapers.com/community/threads/a2-vectors-notes.14125/

and first post of this thread: http://www.xtremepapers.com/community/threads/mathematics-post-your-doubts-here.9599/

Vectors - P3

http://www.xtremepapers.com/community/threads/my-summarized-vector-notes.15200/

 

[2pac]

2pac
check the first post of this thread there are some links to notes for that..

Hey first of all thanks for replying and those notes have really helped me but sadly there is no mention of greatest value of argument there.

 

[smzimran]

what a silly mistake...when taking square of bi i totally forgot i

jazakAllah khairen!!

Wa iyyakum,
Happens sometimes, dont get dishearted!

 

[user]

Hey first of all thanks for replying and those notes have really helped me but sadly there is no mention of greatest value of argument there.

It does:

Complex No. max/min IzI and arg(z) - P3

 

[user]

Wa iyyakum,
Happens sometimes, dont get dishearted!

haha i'm not
thnx though

 

[2pac]

It does:

Complex No. max/min IzI and arg(z) - P3

oh ok thanks,I thought u were talking about the pdf file.

 

[Keitak]

Can someone please explain how to do this type of question. This is the only problem in maths for me, I could never understand how to do it even though I have tried all the past paper questions. I always get the 2nd part wrong.Please post a detailed explanation.
Thank you

 

[Chooi1993]

Next time post the link to the m.s as well!
View attachment 9589
After a long time, as t becomes very large, lets suppose t = 200
e^(t/2) = e^(200/2) = e^100 = very large value so large that adding 5 to it won't make any difference,
So (5 + e^(t/2)) will become equal to e^(t/2)
The numerator and denominator will cancel out and the answer left will be 1800.
You may verify this using a calculator!

Initial value in which question ?
If its the iteration question, take initial value as pie

Q4 P32 the second link