HSC Stuff > HSC Mathematics Extension 2

Remembering Conics Formulae

(1/1)

frog1944:
Hi,

If we remember various formulae for conics such as the equations of tangents, ellipses, chords, and chords of contacts are we allowed to utilise them in the exam? I'm aware if the question specifically asked you to prove the equation for a tangent to an ellipse you can't simply state it. But for questions such as the following:"From what external point are tangents to the ellipse drawn so that is the equation of the chord of contact" (New Senior Mathematics Extension 2 Ex 4.4 Q25)
In the answers it appears as those they just "knew" the general equation for the chord of contact already.

Are we also allowed to quote and use the sum and product of trig functions? (New Senior Mathematics use it in their proof for the equation of the chord on an ellipse and hyperbola)

Thanks

RuiAce:
In general, NO.

Of course, you're obviously going to have to know the equation of an ellipse is \( \frac{x^2}{a^2}+\frac{y^2}{b^2}=1\). But quoting stuff related to tangents and stuff is NOT acceptable unless they give it to you in the exam.

That there, is a textbook. They don't want to make a textbook too massive, so their worked solutions will omit some details. This is NOT reflective of what you should do in the exam.


Sum-to-product has had much debate. I recommend learning the derivations for them instead to be on the safe side (I mean, they are easy to derive).

jakesilove:

--- Quote from: frog1944 on March 13, 2017, 06:21:13 pm ---Hi,

If we remember various formulae for conics such as the equations of tangents, ellipses, chords, and chords of contacts are we allowed to utilise them in the exam? I'm aware if the question specifically asked you to prove the equation for a tangent to an ellipse you can't simply state it. But for questions such as the following:"From what external point are tangents to the ellipse drawn so that is the equation of the chord of contact" (New Senior Mathematics Extension 2 Ex 4.4 Q25)
In the answers it appears as those they just "knew" the general equation for the chord of contact already.

Are we also allowed to quote and use the sum and product of trig functions? (New Senior Mathematics use it in their proof for the equation of the chord on an ellipse and hyperbola)

Thanks

--- End quote ---

Personally, by the time the HSC came around, I'm pretty sure I had memorised most general forms of most things vaguely related to the Maths curriculum. This was just a result of doing so many goddamned questions. However, I would derive them every time, and then use my knowledge to 'check' that I got it right. The main benefit was that, if I somehow got something wrong, I could go back and fudge the numbers until I got a result that I knew to be true. So, knowing the general theorums and results is helpful, but you will need to do the relevant derivations in an exam situation.

frog1944:
Ok, thanks guys :)

Navigation

[0] Message Index