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March 28, 2024, 10:28:09 pm

Author Topic: 3U Maths Question Thread  (Read 1230222 times)  Share 

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RuiAce

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Re: 3U Maths Question Thread
« Reply #555 on: August 10, 2016, 07:55:49 pm »
+1
could you please explain how/why they are the range(s)?


levendibigd

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Re: 3U Maths Question Thread
« Reply #556 on: August 10, 2016, 08:49:59 pm »
0
Could I please have some help with this mathematical induction Q

RuiAce

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Re: 3U Maths Question Thread
« Reply #557 on: August 10, 2016, 08:58:39 pm »
+1
Could I please have some help with this mathematical induction Q






« Last Edit: August 10, 2016, 09:01:33 pm by RuiAce »

levendibigd

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Re: 3U Maths Question Thread
« Reply #558 on: August 10, 2016, 09:59:22 pm »
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Thank you, I really appreciate it!

massive

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Re: 3U Maths Question Thread
« Reply #559 on: August 11, 2016, 12:24:45 am »
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Guys, for part i- how do i show that a limiting sum exists (i got s=cos^2x)
For part ii- how do you do it?
Thanks!

massive

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Re: 3U Maths Question Thread
« Reply #560 on: August 11, 2016, 01:44:44 am »
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Guys i just don't get the last part, where is says "find the equations of the tangent lines to the curve..."

massive

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Re: 3U Maths Question Thread
« Reply #561 on: August 11, 2016, 02:06:10 am »
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Guys again for this I don't get the last part where it says to find the rate at which theta is changing. What i did was find x when theta=pi/4 and sub it into the eqn of part ii and i got 0.2 but the answer is 11 degrees/sec :S

RuiAce

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Re: 3U Maths Question Thread
« Reply #562 on: August 11, 2016, 06:50:52 am »
+1
Guys, for part i- how do i show that a limiting sum exists (i got s=cos^2x)
For part ii- how do you do it?
Thanks!


« Last Edit: August 11, 2016, 07:13:24 am by RuiAce »

RuiAce

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Re: 3U Maths Question Thread
« Reply #563 on: August 11, 2016, 06:57:01 am »
+1
Guys i just don't get the last part, where is says "find the equations of the tangent lines to the curve..."



RuiAce

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Re: 3U Maths Question Thread
« Reply #564 on: August 11, 2016, 07:06:49 am »
+1
Guys again for this I don't get the last part where it says to find the rate at which theta is changing. What i did was find x when theta=pi/4 and sub it into the eqn of part ii and i got 0.2 but the answer is 11 degrees/sec :S
The answer wants it in degrees/sec. Just convert 0.2 rads into degrees by typing in 0.2 * 180/π

jamgoesbam

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Re: 3U Maths Question Thread
« Reply #565 on: August 11, 2016, 11:33:00 am »
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Hi again,
I didn't quite understand part ii) of this question... how did the answer get ln? I thought when integrating (x^2+3)^-0.5 you could use the reverse chain rule so t = (x^2+3)^0.5/(0.5 x 2x). Could someone please explain? Thank you!! :)

jakesilove

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Re: 3U Maths Question Thread
« Reply #566 on: August 11, 2016, 11:55:50 am »
+2
Hi again,
I didn't quite understand part ii) of this question... how did the answer get ln? I thought when integrating (x^2+3)^-0.5 you could use the reverse chain rule so t = (x^2+3)^0.5/(0.5 x 2x). Could someone please explain? Thank you!! :)

Hey!

The thing to note, when doing the reverse chain rule, is that you cannot do it when, inside the brackets, there is a non-linear function. So, you can integrate



But you cannot integrate



using the reverse chain rule. You have to use alternate means, such as the table of standard integrals (as is the case in this question). So, knowing that you can't actually integrate using the reverse chain rule in this case, does the answer described make sense? Like you understand their application of the table of standard integrals?

Great question though!

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jamgoesbam

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Re: 3U Maths Question Thread
« Reply #567 on: August 11, 2016, 12:03:28 pm »
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Hey!

The thing to note, when doing the reverse chain rule, is that you cannot do it when, inside the brackets, there is a non-linear function. So, you can integrate



But you cannot integrate



using the reverse chain rule. You have to use alternate means, such as the table of standard integrals (as is the case in this question). So, knowing that you can't actually integrate using the reverse chain rule in this case, does the answer described make sense? Like you understand their application of the table of standard integrals?

Great question though!

Jake

Ohhhh, yes that's why they used ln!! I didn't know to do this as they don't provide us with the standard table of integrals anymore (since this was from a 2014 paper, before the formula sheet got introduced). But how would you do it without using the table of integrals?

jakesilove

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Re: 3U Maths Question Thread
« Reply #568 on: August 11, 2016, 12:31:34 pm »
+2
Ohhhh, yes that's why they used ln!! I didn't know to do this as they don't provide us with the standard table of integrals anymore (since this was from a 2014 paper, before the formula sheet got introduced). But how would you do it without using the table of integrals?

Ahh okay yeah true, I forgot that you don't get that table anymore! In that case, you can't answer the question, so really don't worry about it :) They can't ask you to integrate that.
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RuiAce

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Re: 3U Maths Question Thread
« Reply #569 on: August 11, 2016, 12:40:25 pm »
+2
Ohhhh, yes that's why they used ln!! I didn't know to do this as they don't provide us with the standard table of integrals anymore (since this was from a 2014 paper, before the formula sheet got introduced). But how would you do it without using the table of integrals?