You are Here: Home

# Vectors - vector equations

Announcements Posted on
Take our survey to be in with the chance of winning a £50 Amazon voucher or one of 5 x £10 Amazon vouchers 28-05-2016
1. Okay, I'm a bit confused here, hoping someone can help clear this up.

The question is "Points A, B and C have co-ords (0, 5), (9, 8) and (4, 3) respectively.
a) Find the vector equation for the line joining A and B.
b) Show that the perpendicular distance from C to line AB is 101/2 "

I understand the vector equation = a + t(b - a), which works out for me as:
(0, 5) + t(9, 3)
But the answer at the back of the book says (0, 5) + t(3, 1)

I'll be able to answer b) once I know how it works out at the above answer.
Any help is appreciated
2. (Original post by Nagillum)
Okay, I'm a bit confused here, hoping someone can help clear this up.

The question is "Points A, B and C have co-ords (0, 5), (9, 8) and (4, 3) respectively.
a) Find the vector equation for the line joining A and B.
b) Show that the perpendicular distance from C to line AB is 101/2 "

I understand the vector equation = a + t(b - a), which works out for me as:
(0, 5) + t(9, 3)
But the answer at the back of the book says (0, 5) + t(3, 1)

I'll be able to answer b) once I know how it works out at the above answer.
Any help is appreciated
is the direction vector, it can be simplified as

It is similar to the gradient, if gradient , this means moving 6 units in the x-direction and 4 units in the y-direction, this is similar to saying move 3 units in the x-direction and 2 units in the y-direction, i.e. Gradient

Hence both vectors are parallel, any of them can be used.

If you are still confused, then plot a point on a graph paper, and then use the vector to get another point on the line, you will see that both represent the same direction.

Hope it makes sense.
3. (Original post by raheem94)
is the direction vector, it can be simplified as

It is similar to the gradient, if gradient , this means moving 6 units in the x-direction and 4 units in the y-direction, this is similar to saying move 3 units in the x-direction and 2 units in the y-direction, i.e. Gradient

Hence both vectors are parallel, any of them can be used.

If you are still confused, then plot a point on a graph paper, and then use the vector to get another point on the line, you will see that both represent the same direction.

Hope it makes sense.
I read the first sentence and went "OOHHHHHHHHHHHHHHHHH!" and now I feel stupid for not seeing that! Yeah I get it, thanks a lot man, 20 to midnight probably isn't the best time to be doing maths, eh :P
4. Your answer to the first part is the same as the one in the book, as the vectors (3,1) and (9,3) point in the same direction. [ (9,3) = 3*(3,1) ]
5. (Original post by RockEater)
Your answer to the first part is the same as the one in the book, as the vectors (3,1) and (9,3) point in the same direction. [ (9,3) = 3*(3,1) ]
Just to confirm something say I had the vector equation:
(4, 12) + t(9, 3)

I WOULD be able to cancel down the (9, 3) as it is a direction vector but I WOULD NOT be able to do this to the (4, 12) because it is a position vector...?
6. (Original post by Nagillum)
Just to confirm something say I had the vector equation:
(4, 12) + t(9, 3)

I WOULD be able to cancel down the (9, 3) as it is a direction vector but I WOULD NOT be able to do this to the (4, 12) because it is a position vector...?
Yes, you can simplify the direction vector but not the position vector.
7. Okay, cheers guys!

## Register

Thanks for posting! You just need to create an account in order to submit the post
1. this can't be left blank
2. this can't be left blank
3. this can't be left blank

6 characters or longer with both numbers and letters is safer

4. this can't be left empty
1. Oops, you need to agree to our Ts&Cs to register

Updated: May 30, 2012
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:
Today on TSR

### Don't be a half-term hermit

How to revise this week and still have a life

Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read here first

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams