is this Q in syllabus? (conics) (1 Viewer)

[Newbie]

P and Q are on the ellipse x^2/a^2 + y^2/b^2 =1
P and Q have parameters theta and phi.

show that if PQ is a focal chord, tan(theta/2)tan(phi/2) equals

-(1-e)/(1+e) or - (1+e)/(1-e)


what the hell is going on here

 

[Richard Lee]

Let point P(asec(theta), btan(theta)) and Q(asec(Phi), btan(phi))
Therefore, the line passes through P and Q:
[y-btan(theta)]/[x-asec(theta)]=[btan(phi)-btan(theta)]/[asec(phi)-asec(theta)]
After that, sub (ae, 0) and (-ae, 0) into the equation, you will get the answer.

Don't forget the trig formula!

 

[Newbie]

Originally posted by Richard Lee
Let point P(asec(theta), btan(theta)) and Q(asec(Phi), btan(phi))
Therefore, the line passes through P and Q:
[y-btan(theta)]/[x-asec(theta)]=[btan(phi)-btan(theta)]/[asec(phi)-asec(theta)]
After that, sub (ae, 0) and (-ae, 0) into the equation, you will get the answer.

Don't forget the trig formula!

dude its an ellipse.....

 

[Richard Lee]

Originally posted by Newbie
dude its an ellipse.....

Thanx!
I am very stupid. Change sec function to cos function and tan function to sin function, plz!
Thank u!

 

[McLake]

I think that is in the syllabus, but it's leaning towards a Q8 ...

 

[Newbie]

ahh ok

anyone wana show me how to do it?

 

[McLake]

Originally posted by Newbie
ahh ok

anyone wana show me how to do it?

I will have to think about it ...

 

[Fosweb]

Scanned because its too much to write up...

 

[freaking_out]

hey, my teacher told me that the sum of trig. functions was taken out of the syllabus, and if they do put it in, they will make u prove it in the first step of the question.

 

[Fosweb]

yeah - thats what our teacher said too. had to look them up. maybe i should learn them anyway? cant hurt.
so i dont know if they'd ask a question like this.

 

[freaking_out]

Originally posted by Fosweb
yeah - thats what our teacher said too. had to look them up. maybe i should learn them anyway? cant hurt.
so i dont know if they'd ask a question like this.

na actually, why don't u check up with the hsc advice line?

 

[Fosweb]

Originally posted by freaking_out
na actually, why don't u check up with the hsc advice line?

lol: i was thinking about doing that. later.

 

[ND]

Fosweb: what did you use to draw that ellipse? Mine always come out looking completely retarded (as with anything else i draw).

 

[freaking_out]

Originally posted by ND
Fosweb: what did you use to draw that ellipse? Mine always come out looking completely retarded (as with anything else i draw).

he's got one of those curve sketching templates.

actually, i have the same problem of my ellipses being retarded...so i betta get one of those templates myself.

 

[ND]

Oh, are they allowed in the exam?

edit: Just saw your thread in 3u, nevermind.

 

[freaking_out]

hey, fosweb, did u use some sort of a template for your handwriting too?