C4 vectors WJEC Watch

Wales 1992
Badges: 0
Rep:
?
#1
Report Thread starter 7 years ago
#1
First post... scary stuff!

I have a past paper question to do for homework but I'm really not sure how to go about it. The question is...

The position vectors of the points A, B and C, relative to a fixed origin O, are 4i + 6j + k, 5i + 8j + 3k and 8i + 2j + 5k, respectively.
Find cos(ABC) [roof on B].

I would be extremely grateful for any help
0
reply
vc94
Badges: 10
Rep:
?
#2
Report 7 years ago
#2
The points A, B and C form a triangle. So to find angle B use the cosine rule.
You'll need to work with the lengths AB, BC and AC.
0
reply
Freerider101
Badges: 12
Rep:
?
#3
Report 7 years ago
#3
(Original post by Wales 1992)
First post... scary stuff!

I have a past paper question to do for homework but I'm really not sure how to go about it. The question is...

The position vectors of the points A, B and C, relative to a fixed origin O, are 4i + 6j + k, 5i + 8j + 3k and 8i + 2j + 5k, respectively.
Find cos(ABC) [roof on B].

I would be extremely grateful for any help
You need to use the dot product formula.
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Latest
My Feed

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.

Personalise

University open days

  • Cranfield University
    Cranfield Forensic MSc Programme Open Day Postgraduate
    Thu, 25 Apr '19
  • University of the Arts London
    Open day: MA Footwear and MA Fashion Artefact Postgraduate
    Thu, 25 Apr '19
  • Cardiff Metropolitan University
    Undergraduate Open Day - Llandaff Campus Undergraduate
    Sat, 27 Apr '19

Have you registered to vote?

Yes! (124)
39.37%
No - but I will (17)
5.4%
No - I don't want to (20)
6.35%
No - I can't vote (<18, not in UK, etc) (154)
48.89%

Watched Threads

View All