conics (1 Viewer)

[JamiL]

when doin conics, there is like a million forumlas that are a kilometer long, do you guys genraly derive them everytime... im talking mainly with reference to finding normal and tangents 2 hyperbolas, or elypses... in cartesian and parametric for,?

 

[turtle_2468]

For me personally, it was handy to remember the ones which are used so commonly it's not worth deriving, then derive the rest. Because I like deriving stuff, I think that meant I just remembered the tangent formula and derived everything else...

but it depends on the person. If you are the kind who prefers to memorise, go and do that... but eventually you will get to a stage where you can't be bothered. I'd say tangent, normal and stuff about focal chords is important... again vary to taste.

 

[Dumsum]

Learn to derive them.

More often than not a question will ask "Show that the equation of the tangent/chord/whatever to the ellipse/hyperbola is this", meaning you have to derive it.

 

[Vampire]

What about things like chord of contact where you have to derive the equation of the tangents as well when proving it. Should you derive that or just memorise it?

 

[turtle_2468]

chord of contact usually pops up either as a derivation or you can assume it...
I'd memorise it but definitely after the ones you're sure to use eg tangent..
although it's sort of a special case because it's really hard to derive off the top of your head...
so I'd say have a vague idea of what it looks like at least

 

[dawso]

remember how 2 derive, remember the formula....that way if u are asked 2 derive, u will know if ur right, and if asked to state, then u can just remember it, if u forget it u can start to derive and then u will remember the form and it will pop out