Parametric Equations :( (1 Viewer)

[nick1048]

Hey fellow BOSers, I'm really sorry I didn't think of this when everyone completed parametrics but I'm seriously lost. It's nothing pedantic I just don't understand the whole concept of the point and directrix... the whole idea of t substitutions... Whilst I can do some questions, these basic facts never allow me to obtain anything above 2/5 for parametric sections.

What I'm basically asking for is any possible resources (no matter how simple or comprehensive) for this topic, as this is causing a void in my mathematical knowledge atm and with the trials and HSC approaching I really want to clear it up. So please, please!!! Anything on parametrics, just post it here or send to nick_1048@hotmail.com

btw thanks a bundle and if you need any help with economics or english I would gladly return the favour.

Regards

 

[FinalFantasy]

the key to solve problems wen u r completely lost like dat is to just go and do lots of questions and ask when u can't do dem...
anyway, the parametrics is pretty much:

Use the formula (y-y1)\(x-x1)=m to get equation of tangents and normals at a poing P(x1,y2)
use the equation of the curve u are given, e.g u might be given x²=4ay
make it y=x²\4a and differentiate it to use as gradient when u use the gradient formula...
know that m1m2=-1, den the lines with gradient m1 and gradient m2 are perpendicular
to find a locus at a point, simply find that point and with those points eliminate the parameters and get the equation, e.g if u have x=2ap, y=ap²
den p=x\2a, y=a(x\2a)²=x²\4a
.: x²=4ay

just use those things and use dem properly, can pretty much take u through da whole parametrics