FP1 question

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  1. sabre2th1's Avatar
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    FP1 question
    So I started doing FP1 and I'm confused..



    Why isn't the argument of z, (pi + alpha) , in the first picture?

    As for the 2nd pic, why isn't the argument of z, (2pi - alpha) ?
  2. Jam''s Avatar
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    Re: FP1 question
    We normally use this thing called the principal argument, such that all arguments are within -\pi \textless arg(z) \leq \pi

    Can you see why these values have been used now? You're technically correct in your thinking and the angles are accurate; it's just something of a convention.
    Last edited by Jam'; 14-07-2012 at 15:37.
  3. Llewellyn's Avatar
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    Re: FP1 question
    The argument could be what you suggest or what is posted. The argument of z is simply the angle from the positive x axis. You could say an argument is pi/2, or you could say an argument is -3pi/2, because that would give you the same angle.

    I have been taught to do it your way, and have a positive angle between 0 and 2pi. However, the approach shown is not incorrect.

    It's pretty much just a matter of style or a convention. Like (sinx)^2 is normally written as sin^2 (x). Neither is wrong, and they both mean exactly the same thing, but one is simply more common.
    Last edited by Llewellyn; 14-07-2012 at 15:33.
  4. TDL's Avatar
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    Re: FP1 question
    (Original post by sabre2th1)
    So I started doing FP1 and I'm confused..



    Why isn't the argument of z, (pi + alpha) , in the first picture?

    As for the 2nd pic, why isn't the argument of z, (2pi - alpha) ?
     -\pi<\theta\leq\pi

    Take a look at page 15.
  5. Jam''s Avatar
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    Re: FP1 question
    In exams they usually want you to give the principal argument, so get into the habit of producing this.
  6. Llewellyn's Avatar
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    Re: FP1 question
    (Original post by Jam')
    In exams they usually want you to give the principal argument, so get into the habit of producing this.
    What board are you on? (or were you on?)
  7. Jam''s Avatar
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    Re: FP1 question
    (Original post by Llewellyn)
    What board are you on? (or were you on?)
    OCR:MEI - bane of my life lol
  8. Blazy's Avatar
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    Re: FP1 question
    (Original post by Jam')
    OCR:MEI - bane of my life lol
    But we have a Differential Equations module !
  9. Jam''s Avatar
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    Re: FP1 question
    (Original post by Blazy)
    But we have a Differential Equations module !
    I wanted to do that. It looked interesting, but my school didn't teach it and I did FM in a year alongside A2 Maths, so I stuck to the familiar Mech and Stats modules - wasn't prepared to do heroics lol.

    Have you just finished AS or A2?
  10. sabre2th1's Avatar
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    Re: FP1 question
    (Original post by Jam')
    We normally use this thing called the principal argument, such that all arguments are within -\pi \textless arg(z) \leq \pi

    Can you see why these values have been used now? You're technically correct in your thinking and the angles are accurate; it's just something of a convention.

    (Original post by Llewellyn)
    The argument could be what you suggest or what is posted. The argument of z is simply the angle from the positive x axis. You could say an argument is pi/2, or you could say an argument is -3pi/2, because that would give you the same angle.

    I have been taught to do it your way, and have a positive angle between 0 and 2pi. However, the approach shown is not incorrect.

    It's pretty much just a matter of style or a convention. Like (sinx)^2 is normally written as sin^2 (x). Neither is wrong, and they both mean exactly the same thing, but one is simply more common.

    (Original post by TDL)
     -\pi<\theta\leq\pi

    Take a look at page 15.
    Thanks, I understand
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