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Parametric Equation

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i) Was good, I got t = (1-x)/x
ii) Was good
iii) I found the y-coordinate as y = 1/(1-t)

question iv) The point Q is the intersection of the line x = 1/2 and the straight line joining the origin to the point T. Point R has co-ordinates (1/2, 0). Show that RQ = QP.

I am completely stuck on how to do this question.
(edited 6 years ago)
Original post by znx


i) Was good, I got t = (1-x)/x
ii) Was good
iii) I found the y-coordinate as y = 1/(1-t)

question iv) The point Q is the intersection of the line x = 1/2 and the straight line joining the origin to the point T. Point R has co-ordinates (1/2, 0). Show that RQ = QP.

I am completely stuck on how to do this question.


Post a better quality image on https://imgur.com/ then post the link here.

The current image is impossible to read.
Reply 2
Original post by RDKGames
Post a better quality image on https://imgur.com/ then post the link here.

The current image is impossible to read.


Yeah sorry for that should be better now.
Original post by znx
Yeah sorry for that should be better now.


This question was asked before: https://www.thestudentroom.co.uk/showthread.php?p=75995584
Reply 4


ah ok thank you :smile:
Reply 5

Thus, the gradient OT is given by , - I thought from ii) that the gradient m is found by dy/dx = -2t/(1-t)^2 ?
Original post by znx
Thus, the gradient OT is given by , - I thought from ii) that the gradient m is found by dy/dx = -2t/(1-t)^2 ?


Yeah that's the gradient along the curve.

OT is not along the curve.
Reply 7
Original post by RDKGames
Yeah that's the gradient along the curve.

OT is not along the curve.

I've still been struggling on the question, I used , and hence the line is
When x = 1/2 I plugged that into the parametric equation to find what t was at the point, however t cant be +/- 1. So I dont really know what to do tbh.
Original post by znx
I've still been struggling on the question, I used , and hence the line is
When x = 1/2 I plugged that into the parametric equation to find what t was at the point, however t cant be +/- 1. So I dont really know what to do tbh.


When x=1/2x=1/2, what is yy in terms of tt?

Then you know the coordinates of the point Q in terms of tt. You also know the coords of R and P. So show that the distances RQ = QP
Reply 9
Original post by RDKGames
When x=1/2x=1/2, what is yy in terms of tt?

Then you know the coordinates of the point Q in terms of tt. You also know the coords of R and P. So show that the distances RQ = QP


So i just sub x =1/2 into that equation for the line?
Original post by znx
So i just sub x =1/2 into that equation for the line?


Well, yeah.

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