Parametrics (1 Viewer)

[frog1944]

Hi,

I have to prove that the ends of a focal chord intersect at right angles on the directrix, though to prove these I need to use the fact that if PQ is a focal chord then, pq=-1. Can I use this in the proof? Or would I have to prove that to? Could I use the knowledge of the equation of chord PQ, I would I similarly have to find and prove that to?

Thanks

 

[InteGrand]

Hi,

I have to prove that the ends of a focal chord intersect at right angles on the directrix, though to prove these I need to use the fact that if PQ is a focal chord then, pq=-1. Can I use this in the proof? Or would I have to prove that to? Could I use the knowledge of the equation of chord PQ, I would I similarly have to find and prove that to?

Thanks

You would probably need to prove these things, otherwise it's assuming too much I think (like the pq = -1 thing is equivalent to saying the chords are perpendicular, which is what we're trying to prove, so assuming pq = -1 for a focal chord is too big an assumption I think).

 

[frog1944]

Ok, thank you very much