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

Core 3 Question Watch

    • Thread Starter
    Offline

    3
    ReputationRep:
    Name:  q1.png
Views: 16
Size:  3.9 KB

    Can someone explain how to do ii part b please.
    Offline

    3
    ReputationRep:
    (Original post by james813)
    Name:  q1.png
Views: 16
Size:  3.9 KB

    Can someone explain how to do ii part b please.
    Notice that \theta = \frac{1}{3}\beta + 20 in the (i) identity gives you the left hand side of the equation. Does this help?
    Offline

    0
    ReputationRep:
    Theta equals 1/3b+20
    Solve in theta terms first using part 1
    Then equate to 1/3 b +20 and solve
    • Thread Starter
    Offline

    3
    ReputationRep:
    (Original post by notnek)
    Notice that \theta = \frac{1}{3}\beta + 20 in the (i) identity gives you the left hand side of the equation. Does this help?
    I think so, thanks.
    So you can substitute it into the answer from part i and solve for beta?
    Offline

    3
    ReputationRep:
    (Original post by james813)
    I think so, thanks.
    So you can substitute it into the answer from part i and solve for beta?
    Yes.
    Offline

    1
    ReputationRep:
    How do you do ii part a?
    Offline

    2
    ReputationRep:
    (Original post by geohan)
    How do you do ii part a?
    Note the question wording, it says details of transformation and this most likely means describing in words.

    It would be helpful if you compare y = R sin(theta + alpha) to

    yB = K x f(x+a).

    Similar to yB's tranformation to f(x), you can say shift left by alpha (this is called phase shift). So, phase shift left by alpha radiants.


    Then, enlarge (1/ R) (if R < 1) or shrink by (1/R) (if R > 1) about theta axis.

    R = (square root of 61 ) / 2

    So, in this case, shrink y values by (2 / (square root of 61 )) factor about theta axis.

    I think this is what the examiner is expecting.

    On the otherhand, you might be expected express transformation in algebraic form where possible, like
    f(x+a) = f(x) - a
    Offline

    2
    ReputationRep:
    (Original post by geohan)
    How do you do ii part a?
    Note the question wording, it says details of transformation and this most likely means describing in words.

    It would be helpful if you compare y = R sin(theta + alpha) to

    yB = K x f(x+a).

    Similar to yB's tranformation to f(x), you can say shift left by alpha (this is called phase shift). So, phase shift left by alpha radiants.


    Then, enlarge (1/ R) (if R < 1) or shrink by (1/R) (if R > 1) about theta axis.

    R = (square root of 61 ) / 2

    So, in this case, shrink y values by (2 / (square root of 61 )) factor about theta axis.

    I think this is what the examiner is expecting.

    On the otherhand, you might be expected express transformation in algebraic form where possible, like
    f(x+a) = f(x) - a
    Offline

    2
    ReputationRep:
    Alternatively you could expand the cos(theta - 60) using double angle formulae, then simplify using values for cos(60), etc.
    Offline

    2
    ReputationRep:
    (Original post by TIF141)
    Alternatively you could expand the cos(theta - 60) using double angle formulae, then simplify using values for cos(60), etc.
    If you mean it for (i), then that's fine.

    Very carefully read the question, the emphasis is on the word "Hence".

    So, you are expected to use the previous results and answering the question is a form of mathematical deduction process (like induction process).

    Therefore, I think expanding will not accepted by examiner.

    If the wording is "Hence or otherwise", then it is reasonable to use cos (A+B) expansion.
 
 
 
Poll
Should gherkins be in burgers?
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

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