HSC 2012 d)i) (1 Viewer)

[andybandy]

Why is it that we have to use Pythagoras’ theorem to show p lies on the parabola, give parametricaly by ...
Couldn't we just substitute the values for p in ?

 

[superSAIyan2]

do you mean sub P (t,y) into the parametric eqns x=t and y=t^2/k? That wont work for y; you must first show there is a relation between y and k.

I think pythagoras is the only way to get a relationship between y and k, since you are given the triangle is right angled.
It doesnt take that long. Only 3 or 4 lines

 

[andybandy]

Yes thats the question, its not about the lines, but can you explain to my why that pythagoras gets the relationship between y and k ?
Edit: DW i got it!! thankyou!