Conics (1 Viewer)

richz

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For conics questions like questions from cambridge ex 3.3, similar triangles can be used instead of ridiculous algebra. Does anyone know where this information is from? Cuz my teacher doesnt really accept it, i want to show the proof or some sorta evidence so i could use it for a test. thnx :D

PS Can it be used for the HSC?? My guess is yes, since so many past people have done it.
 

FinalFantasy

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u can use similar triangles for some stuff, e.g it can be used for part of the proof in da q. where u have to prove that the lines from foci to tangent and normal are equally inclined... something like dat.

of course it can be used in da HSC, as long as u do it properly
 

haboozin

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any mathemtically correct way of obtaining an answer is concidered correct in the HSC....

however, u cant just plug in certain formula's like physics ones for projectile...

If you can show how to get the answer then thats fine...
Just because your doing Q's in conics chapter doesnt matter you have to solve them that way..
Many Q's in the hsc have a few solutions and in a number of cases one solution is some sort of geometry instead of algebra and they are 100% accepted...


I just did 3.3 :p
well Q 1 to 7...
i used midpoint of Q7 if that counts?
 

dawso

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most conics questions involve an initial discovery using conic theory and then 2 prove a result use other mathematics, such as co ordinate geometry, or even complex numbers (deriving rec. hyp formula) and even polynomials, almost everything, another thing is similar triangles, as FF said, the proof that the tangents are equally inclined to the focal chords relies on similar triangles, other places where it could be used include.....

*lines are parallel (derive similar triangles and therefore corresponding triangles, one will be given as perp.)

*to derive a ratio of sides say one i think has prove.....PR/PS = ab
u can use a combination of eccentricity rules and similar triangles to get a series of fractions to work with

basically, draw a diagram and look at the easiest approach, dont just think because its conics u have to use conic theory, it may be far simpler, more practise wil help u see where 2 use what

cheers

-dawso
 

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