Turn on thread page Beta
    • Community Assistant
    • Thread Starter
    Offline

    15
    ReputationRep:
    Community Assistant
    will upload question image in a min
    • Community Assistant
    • Thread Starter
    Offline

    15
    ReputationRep:
    Community Assistant
    will post
    • Community Assistant
    • Thread Starter
    Offline

    15
    ReputationRep:
    Community Assistant
    Name:  123.PNG
Views: 8
Size:  42.8 KB
    part c

    I get confused as in questions that I have seen they mention that

    find the smallest positive value for this maximum occurs or minimum but here they don't
    • Community Assistant
    Offline

    20
    ReputationRep:
    Community Assistant
    (Original post by Qer)
    part c

    I get confused as in questions that I have seen they mention that

    find the smallest positive value for this maximum occurs or minimum but here they don't
    Well here they're not interested in max/min, they're interested in a specific value which is 2.
    The only difference between the two forms is the -ve sine, which means that instead of R \cos (\theta - \alpha) you now get R \cos (\theta + \alpha) instead. Meaning you just have to add on 2\alpha to all your solutions from part (b) and pick the smallest positive one.
    • Community Assistant
    • Thread Starter
    Offline

    15
    ReputationRep:
    Community Assistant
    (Original post by RDKGames)
    Well here they're not interested in max/min, they're interested in a specific value which is 2.
    The only difference between the two forms is the -ve sine, which means that instead of R \cos (\theta - \alpha) you now get R \cos (\theta + \alpha) instead. Meaning you just have to add on 2\alpha to all your solutions from part (b) and pick the smallest positive one.
    Can you please explain me why to add 2a(alpha)? I don't understand that point:confused:
    • Community Assistant
    • Thread Starter
    Offline

    15
    ReputationRep:
    Community Assistant
    (Original post by Qer)
    Can you please explain to me why er have to add 2a(alpha)? I don't understand that point:confused:

    edit: is that due to this reason that if we add 2alpha in
    cos(theta -alpha) we get cos(theta + alpha)?
    • Community Assistant
    Offline

    20
    ReputationRep:
    Community Assistant
    (Original post by Qer)
    edit: is that due to this reason that if we add 2alpha in
    cos(theta -alpha) we get cos(theta + alpha)?
    Apologies, I meant subtract 2\alpha from all your solutions

    Though yes, you're on the right lines. If we replace \theta by \theta + 2\alpha then our equation R\cos (\theta - \alpha) (1) becomes R\cos (\theta + \alpha) (2) and the solutions to eq.(1) are of the form \theta = (...) which become \theta + 2\alpha = (...) hence the solutions to eq.(2) are just \theta = (...) - 2\alpha
    • Community Assistant
    • Thread Starter
    Offline

    15
    ReputationRep:
    Community Assistant
    (Original post by RDKGames)
    Apologies, I meant subtract 2\alpha from all your solutions

    Though yes, you're on the right lines. If we replace \theta by \theta + 2\alpha then our equation R\cos (\theta - \alpha) (1) becomes R\cos (\theta + \alpha) (2) and the solutions to eq.(1) are of the form \theta = (...) which become \theta + 2\alpha = (...) hence the solutions to eq.(2) are just \theta = (...) - 2\alpha

    I understood now

    thankyou
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: February 15, 2018
The home of Results and Clearing

1,198

people online now

1,567,000

students helped last year

University open days

  1. Bournemouth University
    Clearing Open Day Undergraduate
    Wed, 22 Aug '18
  2. University of Buckingham
    Postgraduate Open Evening Postgraduate
    Thu, 23 Aug '18
  3. University of Glasgow
    All Subjects Undergraduate
    Tue, 28 Aug '18
Poll
How are you feeling about GCSE results day?
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.