Hey there! Sign in to join this conversationNew here? Join for free
x Turn on thread page Beta

Please help with vectors (I feel like it should be easy, but still can't get it) watch

    • Thread Starter
    Offline

    14
    ReputationRep:
    I showed c.c' = 0 and I can't figure out the very last part. Any help is much appreciated.

    EDIT: After hours of trying different combinations of substitutions I got it. My solution was really lengthy though. I first showed a^2 + a'^2 = b^2 + b'^2 which was alright and then that a^2 + a'^2 = c^2 + c'^2 which took a whole page of long lines. Anyone know a better/easier/quicker way?
    I started by saying a.a' = b.b' and doing substitutions until I got the result and then the same thing with
    a.a' = c.c' which as I said took ages.
    Even if this is the right way, I had to do so many random combinations of substitutions until I got it and this doesn't seem very mathematical. Any other ideas? Thanks
    Attached Images
     
    Offline

    13
    ReputationRep:
    (Original post by monk1324)
    I showed c.c' = 0 and I can't figure out the very last part. Any help is much appreciated.

    EDIT: After hours of trying different combinations of substitutions I got it. My solution was really lengthy though. I first showed a^2 + a'^2 = b^2 + b'^2 which was alright and then that a^2 + a'^2 = c^2 + c'^2 which took a whole page of long lines. Anyone know a better/easier/quicker way?
    I started by saying a.a' = b.b' and doing substitutions until I got the result and then the same thing with
    a.a' = c.c' which as I said took ages.
    Even if this is the right way, I had to do so many random combinations of substitutions until I got it and this doesn't seem very mathematical. Any other ideas? Thanks
    Try expanding  \bf{(a - a' ) . (a - a' )} and then notice that \bf{(a - a' ) = (b - b' ) }
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: October 19, 2015
Poll
Do you agree with the proposed ban on plastic straws and cotton buds?
Useful resources

Make your revision easier

Maths

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

Equations

How to use LaTex

Writing equations the easy way

Student revising

Study habits of A* students

Top tips from students who have already aced their exams

Study Planner

Create your own Study Planner

Never miss a deadline again

Polling station sign

Thinking about a maths degree?

Chat with other maths applicants

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.