Hey there! Sign in to join this conversationNew here? Join for free
 You are Here: Home >< Maths

# FP1 Watch

1. Why is the equation of the tangent passing through X and P (from part a) not the same as the line passing through X and P
3F Question 10d equation of XP
https://644625398389466aee0063322305...0NRNU0/CH3.pdf
2. (Original post by Acrux)
Why is the equation of the tangent passing through X and P (from part a) not the same as the line passing through X and P
3F Question 10d equation of XP
https://644625398389466aee0063322305...0NRNU0/CH3.pdf
They are the same - just using different parameters.

We have a=ct, so t=a/c. Substitute that into the first equation for the tangent, and you end up with the second equation.

Method used in the markscheme is a bit round the houses, IMO.
3. (Original post by ghostwalker)
They are the same - just using different parameters.

We have a=ct, so t=a/c. Substitute that into the first equation for the tangent, and you end up with the second equation.

Method used in the markscheme is a bit round the houses, IMO.
wait so what do i do?
put a/c in tangent x+t^2y=2ct
4. (Original post by Acrux)
wait so what do i do?
put a/c in tangent x+t^2y=2ct
Yep. Just substitute a/c for t in that equation, and you'll get their second equation.
5. (Original post by ghostwalker)
Yep. Just substitute a/c for t in that equation, and you'll get their second equation.
I got ya^2=2a-c^2x
rearragned to get

Actually y=-c^2x/a^2 + 2c^2/a
is this correct ghostwalker
6. (Original post by Acrux)
I got ya^2=2a-c^2x
rearragned to get

Actually y=-c^2x/a^2 + 2c^2/a
is this correct ghostwalker
Take out the factor as per the markscheme, and you can see for yourself.

Reply
Submit reply
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: April 27, 2016
Today on TSR

### What is the latest you've left an assignment

And actually passed?

### Simply having a wonderful Christmas time...

Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• Poll
Useful resources

## Make your revision easier

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams

Can you help? Study help unanswered threads

## Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.