Join TSR now and get all your revision questions answeredSign up now

Simple Vectors Triangle Rule Question!

    • Thread Starter

    It has been a few years since I have had to look at vectors, but I have got stuck on the first page of my textbook, and there is no working out in there to help me. Any help would be greatly appreciated.

    The magnitudes of the vectors shown are ¦U¦ = 8 and ¦V¦ = 3. The vector V is vertical. The vector U goes up at a 45 degree angle. Graphically determine the magnitude of the vector U-2V.

    Answer: 5.7

    Now the triangle rule states that I should use U-V. However that doesn't give the right answer.

    I tried using the sin and cosine rules to get there by doing sin(45)/6=sin(x)/8 and going from there but that does not give me the right answer either.

    Am I going wrong? please help! Thank you!

    Just draw it like this and apply the cosine rule. You should get the right answer.

    Name:  VECTOR.PNG
Views: 17
Size:  2.8 KB
Which party will you be voting for in the General Election 2017?
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

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

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