Hey there! Sign in to join this conversationNew here? Join for free
    • Thread Starter
    Offline

    0
    ReputationRep:
    I understand the method of how to express something in the wave form however there is one small stage I'm having difficulties getting right and I don't understand what it is I actually do.

    When I have to expand the likes of kcos(x-a), how do I do it? Where does the sin come from? I can do the rest but I keep making mistakes here with the positive and negatives. Can someone just tell me exactly what is being done when this wave form is expanded, what are you actually doing? I think if I can see how to expand it step-by-step will stop making mistakes.

    Just so you know what I mean:

    When I expand kcos(x-a) how do I know it's not:

    1. k(cosxcosa - sinxsina) or
    2. k(cosxsina - cosasinx) or
    3. k(cosxcosa + sinxsina) or
    4. k(cosxsina + cosasinx)

    how do I expand it correctly? What am I actually multiplying together! Please help!! Thanks
    Offline

    2
    ReputationRep:
    It is on the formula sheet so you don't need to memorise them

    But for this case it is, k(cosxcosa + sinxsina)
    Offline

    2
    ReputationRep:
    You are over-thinking this, it's just the double-angle formulae with a k stuck on the side.
 
 
 
  • 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.

  • Poll
    Has a teacher ever helped you cheat?
    Applying to university
  • 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.

  • 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.