velox
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I officially suck at parametrics, well at least i think so.. Are their standard questions that are usually asked in preliminaries? Im cramming it, and need to know what i can 'leave' out and what i cant..any tips will be great.
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Parametrics (1 Viewer)
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mishka
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join the club... although i did get full marks for a parametric question in the trial so i was cheerin'!!
i don't think anything can be "left out" - you should be able to prove all the results - that's how i remember them... it seems to be easier for me to remember the proofs rather than memorise some equation...
i don't think anything can be "left out" - you should be able to prove all the results - that's how i remember them... it seems to be easier for me to remember the proofs rather than memorise some equation...
nick1048
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the trick is the locus problems :\ bah... its like degree four polynomials and trying to establish some pattern
velox
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i can prove all the results except for the equation of a chord. We never learnt the two point formula....Anyone care to enlighten me?
nick1048
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you don't need the 2 point formula... use
y - y1 = m(x - x1)
y - y1 = m(x - x1)
velox
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thats not the two point formula mishka!
velox
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how do u apply that to the equation of a chord derivation?nick1048 said:
Two pt formula is simply (y-y1)/(x-x1)=(y2-y1)/(x2-x1)
i.e. pt and gradient formula as quoted above, but with m expanded.
They probably didn't teach you it as it's more error prone.
To derive eq chord, m=(ap^2-aq^2)/(2ap-2aq), factorise, and then shove in pt and gradient formula [or use two pt formula]
i.e. pt and gradient formula as quoted above, but with m expanded.
They probably didn't teach you it as it's more error prone.
To derive eq chord, m=(ap^2-aq^2)/(2ap-2aq), factorise, and then shove in pt and gradient formula [or use two pt formula]
velox
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sweet thanks, got it now
Li0n
spiKu
say if the question doesn't ask for anything in specific (eg, gradient of chord PQ being (p+q)/2) could you just say that and work out from there to answer the question.
Especially for equation of a chord from a point of contact ( i hope there hasn't been any questions asking for the derivation of this )
Especially for equation of a chord from a point of contact ( i hope there hasn't been any questions asking for the derivation of this )
mishka
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i never posted that formula!! it was nick1048.... jeezwrx said:
but now you know what it is and that's all that matters!! good luck!!
edit: arrgghhhh... got it... i don't read things properly!!! at least estel knows what's going on... i'm going to shut up now!!
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nick1048
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lmao, your trying to help dont feel bad XD XD, I gotta study this gunk for my prelim yearly on friday... yuck! But for now I'm concentrating on perfecting 2unit
Li0n
spiKu
not for chord of contact... but common sense agrees with youXayma said:
Another question.
Say if the question gives you the values of t1 and t2 or just gives you coordinates are you allowed to work with x^2 = 4ay and P(2ap,ap^2) then at the end say since a = 1/4 or whatever etc etc then sub in the correct stuff, or do you have to work with the proper values at the start.
I hate working with numbers >.<
velox
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yeah i learnt how to derive all of them. Its easier than remembering the formula imo.
Li0n
spiKu
Hmm i don't see why not though, it still works out at the end.Estel said:
another question.
say if you just found something for p
eg
ii) proove that the equation of the normal at P is given by x + py = 2ap + ap^3
once you proove that and later on you need the eqn of the normal at Q can you just go Similarly, x + qy = 2aq + aq^3
my teacher said you could but she aint a hsc marker.
Because it's not mathematically sound!
If you can justify it, then you can use it. Give an example, I don't really see how you can prove if something works for one value, it works for all.
As for your q, yes you may, but say it straight after you say the normal of P, otherwise it doesn't make sense (i.e. similarly to what?).
If you can justify it, then you can use it. Give an example, I don't really see how you can prove if something works for one value, it works for all.
As for your q, yes you may, but say it straight after you say the normal of P, otherwise it doesn't make sense (i.e. similarly to what?).