# Thread: Remembering Formulae for Conics

1. ## Remembering Formulae for Conics

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 $\frac{x^2}{8}+\frac{y^2}{6}=1$ drawn so that $x-y+2=0$ 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.

Thanks

2. ## Re: Remembering Formulae for Conics

Generally,

It is a good idea to remember the equation of the tangent to ellipse and hyperbola. Either they give u normal or u prove it so no point remembering that. Chord of Contact isn't used that often but you should probably remember that in case.

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