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March 30, 2024, 12:38:26 am

Author Topic: 3U Maths Question Thread  (Read 1230701 times)  Share 

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FallonXay

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Re: 3U Maths Question Thread
« Reply #870 on: October 23, 2016, 07:55:40 pm »
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P is the point of intersection at the x-axis.





Therefore C is the correct answer, as it is the second intercept.
Personally, for questions like this, I would just sub values in for t and see which one gives you zero. You'll find that only A and C do, however A would be the first intercept (as it is smaller) making C the second intercept, and our answer. Otherwise, use the general solution on your formula sheet to do this formally

I see - Thanks Jake and Syndicate! :)
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imtrying

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Re: 3U Maths Question Thread
« Reply #871 on: October 23, 2016, 08:15:23 pm »
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Hey:) Just revising the inverse functions topic - what would cos^-1 (-x) derive to? (its the fact that x is negative that' s got me confused)
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RuiAce

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Re: 3U Maths Question Thread
« Reply #872 on: October 23, 2016, 08:21:03 pm »
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Hey:) Just revising the inverse functions topic - what would cos^-1 (-x) derive to? (its the fact that x is negative that' s got me confused)


jakesilove

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Re: 3U Maths Question Thread
« Reply #873 on: October 23, 2016, 08:24:55 pm »
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This is why I prefer the relationship



And associated formula for inverse trig. Just covers all your bases :)
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RuiAce

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Re: 3U Maths Question Thread
« Reply #874 on: October 23, 2016, 08:26:09 pm »
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This is why I prefer the relationship



And associated formula for inverse trig. Just covers all your bases :)
Isn't that formula just the chain rule applied to a generic f(x)

imtrying

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Re: 3U Maths Question Thread
« Reply #875 on: October 23, 2016, 08:28:20 pm »
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This is why I prefer the relationship



And associated formula for inverse trig. Just covers all your bases :)



Thanks!
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jakesilove

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Re: 3U Maths Question Thread
« Reply #876 on: October 23, 2016, 08:28:29 pm »
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Isn't that formula just the chain rule applied to a generic f(x)

Yep, and there are similar(ly easy) formulas you can either memorise/use the chain rule for in terms of sin and tan, I just think it's misleading to chuck the formula on the formula sheet that is barely ever useful without teaching (because most teachers don't teach) the specific use of the chain rule for inverse trig.
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RuiAce

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Re: 3U Maths Question Thread
« Reply #877 on: October 23, 2016, 08:30:13 pm »
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Yep, and there are similar(ly easy) formulas you can either memorise/use the chain rule for in terms of sin and tan, I just think it's misleading to chuck the formula on the formula sheet that is barely ever useful without teaching (because most teachers don't teach) the specific use of the chain rule for inverse trig.
Hm fair enough. Now that you mention it I don't think I was taught it either.

Good thing is though, I spent 15 or so minutes learning how to actually use dy/dx = dy/du du/dx, so that if I was ever too lost I could go all the way back there.

Pretty handy when you have to do something like this

jakesilove

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Re: 3U Maths Question Thread
« Reply #878 on: October 23, 2016, 08:32:40 pm »
+1
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Re: 3U Maths Question Thread
« Reply #879 on: October 23, 2016, 08:33:08 pm »
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Hm fair enough. Now that you mention it I don't think I was taught it either.

Good thing is though, I spent 15 or so minutes learning how to actually use dy/dx = dy/du du/dx, so that if I was ever too lost I could go all the way back there.

Pretty handy when you have to do something like this


This is why I love Maple
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Re: 3U Maths Question Thread
« Reply #880 on: October 23, 2016, 08:33:50 pm »
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WolframAlpha and MATLAB. All I really need.

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Re: 3U Maths Question Thread
« Reply #881 on: October 23, 2016, 08:34:45 pm »
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Hey, thank you so much but is there a clearer way because I can't seem to understand what your saying. Sorry about that.

RuiAce

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Re: 3U Maths Question Thread
« Reply #882 on: October 23, 2016, 08:38:45 pm »
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Hey, thank you so much but is there a clearer way because I can't seem to understand what your saying. Sorry about that.
Indicate where you are lost. That is the most efficient way possible.

(Also, note that another approach is just to use brute force to expand both the LHS and RHS of what you want to prove. Less efficient but in general recommended if you just started induction.)
« Last Edit: October 23, 2016, 08:44:35 pm by RuiAce »

imtrying

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Re: 3U Maths Question Thread
« Reply #883 on: October 23, 2016, 08:40:51 pm »
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I was able to get the answer for this one (B) just by subbing in values, but just wondering if there's a better way to work out this kind of question, just in case subbing in values isnt going to work?
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Re: 3U Maths Question Thread
« Reply #884 on: October 23, 2016, 08:43:43 pm »
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I was able to get the answer for this one (B) just by subbing in values, but just wondering if there's a better way to work out this kind of question, just in case subbing in values isnt going to work?