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

# vectors watch

1. Why is this wrong... ??
Attached Images

2. (Original post by pippabethan)
Why is this wrong... ??
It's not wrong, you've just found the obtuse angle between the two lines, the question wants the acute angle.
3. (Original post by Zacken)
It's not wrong, you've just found the obtuse angle between the two lines, the question wants the acute angle.
Now that was a quick response.
4. (Original post by Zacken)
It's not wrong, you've just found the obtuse angle between the two lines, the question wants the acute angle.
Okay, thank you! I was worried I didn't understand it properly! How do I 'translate' this into the angle they want?
5. (Original post by pippabethan)
Okay, thank you! I was worried I didn't understand it properly! How do I 'translate' this into the angle they want?
Well, you have and you know is obtuse, so you really want
6. (Original post by Zacken)
Well, you have and you know is obtuse, so you really want
Thank you so much! I (eventually) got there! Just to speed up my working in the exam, is there a slightly different way I could approach this to obtain the acute angle originally?
7. (Original post by pippabethan)
Thank you so much! I (eventually) got there! Just to speed up my working in the exam, is there a slightly different way I could approach this to obtain the acute angle originally?
Not really. Unless you could see that if you took AB and AC and their dot product was negative. Then you can use BA and AC or AB and CA to get a positive dot product.
8. (Original post by Zacken)
Not really. Unless you could see that if you took AB and AC and their dot product was negative. Then you can use BA and AC or AB and CA to get a positive dot product.
Ah right, I might try that in the future

Reply
Submit reply
Turn on thread page Beta
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: May 21, 2016
Today on TSR

### Congratulations to Harry and Meghan!

But did you bother to watch?

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

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

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