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March 28, 2024, 11:55:50 pm

Author Topic: 3U Maths Question Thread  (Read 1230241 times)  Share 

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teapancakes08

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Re: 3U Maths Question Thread
« Reply #825 on: October 22, 2016, 08:13:34 pm »
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Let me lend a hand! So you are correct, T is essential, since it has the coordinates we need. But we want more information to help eliminate our parameters.

Let's try and use the new info we were given. Let's look at the gradient of PQ:



But it passes through (0,6a), so let's get another expression for that:



Equating these:



So this is a new bit of information for us to use to find our locus! Remember, the idea is to tie x and y back in to the T coordinates. Let me show you; start by considering the y-coordinate:




And actually, believe it or not, that's it. We have an equation that defines a set of points that obey the given conditions! Any point on the line \(y=-4a\) will satisfy our requirements, and so THAT is the locus of the Point T :)

Ah, I see – so you find the gradients and then simplify your way through. Although...I'm little confused as how (p^2 – 6)/2p = (p+q)/2 simplified into -2/p = q/2 . But other than that I understand how to do it now. Thanks so much for the explanation ;D
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RuiAce

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Re: 3U Maths Question Thread
« Reply #826 on: October 22, 2016, 08:18:27 pm »
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Ah, I see – so you find the gradients and then simplify your way through. Although...I'm little confused as how (p^2 – 6)/2p = (p+q)/2 simplified into -2/p = q/2 . But other than that I understand how to do it now. Thanks so much for the explanation ;D
I think that should be -3/p there, not -2/p

jamgoesbam

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Re: 3U Maths Question Thread
« Reply #827 on: October 22, 2016, 09:09:36 pm »
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Hi there! Could someone please explain part e)? Would be much appreciated! :)

teapancakes08

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Re: 3U Maths Question Thread
« Reply #828 on: October 22, 2016, 09:36:27 pm »
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I think that should be -3/p there, not -2/p

That...makes more sense, actually. Although I'm still not sure how it simplifies into -3/p = q/2...
I did, however, get the answer:



By the messy working out below. Would it be okay to write it like that?
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RuiAce

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Re: 3U Maths Question Thread
« Reply #829 on: October 22, 2016, 09:41:36 pm »
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That...makes more sense, actually. Although I'm still not sure how it simplifies into -3/p = q/2...
I did, however, get the answer:



By the messy working out below. Would it be okay to write it like that?

RuiAce

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Re: 3U Maths Question Thread
« Reply #830 on: October 22, 2016, 09:44:43 pm »
+1

teapancakes08

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Re: 3U Maths Question Thread
« Reply #831 on: October 22, 2016, 10:09:20 pm »
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I see. To be honest, I tried figuring out how to unpack Jamon's method but ended up getting frustrated because some figures wouldn't cancel out (cumulated in a page of crossed out working out). It genuinely slipped my mind that you could separate them into separate terms...something that tends to happens a lot. I probably should go do more practice then, huh...

Thanks for the help  ^^
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RuiAce

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Re: 3U Maths Question Thread
« Reply #832 on: October 22, 2016, 10:14:13 pm »
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I see. To be honest, I tried figuring out how to unpack Jamon's method but ended up getting frustrated because some figures wouldn't cancel out (cumulated in a page of crossed out working out). It genuinely slipped my mind that you could separate them into separate terms...something that tends to happens a lot. I probably should go do more practice then, huh...

Thanks for the help  ^^
All good. If you tend to run into little mistakes/mishaps though, you should make a list of them. And then look at those before you walk into the exam room.

chloe9756

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Re: 3U Maths Question Thread
« Reply #833 on: October 22, 2016, 10:37:47 pm »
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question im stuck on:

1. Consider the series 1+ 2/2 + 3/4 +4/8 +5/16 + 6/32 + ...

a) write out the terms of Sn and 2Sn.

b) subtract to get an expression for Sn.

c) find the limit as n approaches infinity and hence find limiting sum.

RuiAce

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Re: 3U Maths Question Thread
« Reply #834 on: October 22, 2016, 10:52:03 pm »
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MagmaMeerkat

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Re: 3U Maths Question Thread
« Reply #835 on: October 22, 2016, 11:01:36 pm »
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Multiple choice question:
Which expression is equal to cos(x) - sin(x)?
A) (root2) cos(x+pi/4)
B) (root2) cos(x-pi/4)
C) (2) cos(x+pi/4)
D) (2) cos(x-pi/4)

And please explain how you can work it out/derive it?

RuiAce

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Re: 3U Maths Question Thread
« Reply #836 on: October 22, 2016, 11:03:31 pm »
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Multiple choice question:
Which expression is equal to cos(x) - sin(x)?
A) (root2) cos(x+pi/4)
B) (root2) cos(x-pi/4)
C) (2) cos(x+pi/4)
D) (2) cos(x-pi/4)

And please explain how you can work it out/derive it?

Sanaz

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Re: 3U Maths Question Thread
« Reply #837 on: October 22, 2016, 11:37:40 pm »
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Can anyone help me with this?


RuiAce

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Re: 3U Maths Question Thread
« Reply #838 on: October 22, 2016, 11:41:40 pm »
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WLalex

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Re: 3U Maths Question Thread
« Reply #839 on: October 23, 2016, 11:27:29 am »
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Help with part (iii) please..I got an expression in terms of n, n+1, n+2 and (1/2) but can't figure out how to manipulate it into what the answers wants
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