Turn on thread page Beta
    • Thread Starter
    Offline

    6
    ReputationRep:
    Can someone please help me on these Vectors questions from C4?? I am majorly stuck!! :confused:

    Q1) Referred to a fixed origin, the line L1 has the equation r=12i+15j+k+s(2i+j+k) and the line L2 has the equation r=i+j-2k+t(3i-k)

    a) Show that the lines L1 and L2 intersect and find the position vector of A, their point of intersection

    b) Find, to the nearest degree, the acute angle between the lines L1 and L2

    The point B with position vector 16i+7j+3k lies on the line L1. The point C with position vector 22i+j-9K and the point D both lie on the line L2.

    c)Given that BD is perpendicular to AC, find the position vector of D

    d)Hence, or otherwise, prove that ?ABC is isosceles

    Thank you for the help in advance....I REALLY APPRECIATE IT!!
    Offline

    10
    ReputationRep:
    1) Equate the two lines to form 3 equations in 2 unknowns, s and t. Solve one pair and you must verify the third equation.
    2) Use formula cos(theta) = (a.b)/(|a|*|b|), just remember to use the direction vectors of each line.
    3) Perpendicular means the dot product is equal to zero...
    • Thread Starter
    Offline

    6
    ReputationRep:
    (Original post by vc94)
    1) Equate the two lines to form 3 equations in 2 unknowns, s and t. Solve one pair and you must verify the third equation.
    2) Use formula cos(theta) = (a.b)/(|a|*|b|), just remember to use the direction vectors of each line.
    3) Perpendicular means the dot product is equal to zero...
    Thanks for the help....I seriously appreciate it
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: March 27, 2011

University open days

  1. University of Bradford
    University-wide Postgraduate
    Wed, 25 Jul '18
  2. University of Buckingham
    Psychology Taster Tutorial Undergraduate
    Wed, 25 Jul '18
  3. Bournemouth University
    Clearing Campus Visit Undergraduate
    Wed, 1 Aug '18
Poll
How are you feeling in the run-up to Results Day 2018?
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.