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  1. B

    Rounding up/down years in exponentials

    For a start, if the question does say "find the number of years", there is no need to round. It is not asking for a whole number of years. The exception is if something is increasing on a specific date every year. But then it is not exponential growth because the growth is not continuous - it is...
  2. B

    The integration of e^(-x^2)

    I don't know. Someone once suggested that to me - that is all.
  3. B

    Calling any Abbotsleigh 2015 students

    Will your little sister beat you up if you distribute the paper?
  4. B

    The integration of e^(-x^2)

    Is he really a "he" ? I had heard otherwise.
  5. B

    100% in 4u maths?

    So when I look at the state rankings, how will I know if this person is on the list?
  6. B

    Calling any Abbotsleigh 2015 students

    I think I finally figured out your name. I'm guessing you won't be doing any study after 5:45 this afternoon?
  7. B

    The integration of e^(-x^2)

    Ahhh .... so no-one can tell you've been visiting the Neighbours and Home and Away forums?
  8. B

    The integration of e^(-x^2)

    Just wondering why the little light next to your name never comes on to indicate you are logged in?
  9. B

    The integration of e^(-x^2)

    I think it's simpler to think of it as coming from l=rθ The area of a thin annular sector is approximately equal to the arc length times the change in radius.
  10. B

    The integration of e^(-x^2)

    Check out this link: https://www.youtube.com/watch?v=nqNzKeVCYBU But ... you will need to understand double integrals and polar coordinates.
  11. B

    The integration of e^(-x^2)

    Is that an "if and only if" statement?
  12. B

    The integration of e^(-x^2)

    Hmmm ... my quote looks kind of stupid out of context.
  13. B

    The integration of e^(-x^2)

    You don't need to sub in -inf to inf. Integrating from -3 to 3 gives 99.998% of the total value. The number of terms you add has a much bigger effect on the estimate than the size of the limits.
  14. B

    America or Australia?

    Well it IS the gun-toting, bible-thumping, execution-loving, war-mongering, serial-killer-producing US of A.
  15. B

    America or Australia?

    Ummm ..... you seem to be confusing terrorist attacks with gun massacres by a madman.
  16. B

    The integration of e^(-x^2)

    And ... a derivation of E=mc^2
  17. B

    The integration of e^(-x^2)

    Can people see how the constant/linear terms in the Taylor expansion gives the equation of the tangent at the origin? For sinx it is y=x. For cosx it is y=1. For e^x it is y=1+x.
  18. B

    Coordinate geometry question

    Oops - just reread - you CAN do part (a). For (ii), perhaps use the fact that the x and y coords are actually the t-formulae. But it still gets way too messy for 2 marks.
  19. B

    Coordinate geometry question

    If you know that A lies on the given circle, then you already know the answer to part (a). If you need the working: x^2+y^2=\frac{\left(1-a^2\right)^2+(2a)^2}{\left(1+a^2\right)^2} =\frac{1-2a^2+a^4+4a^2}{\left(1+a^2\right)^2} =\frac{1+2a^2+a^4}{\left(1+a^2\right)^2}...
  20. B

    Find itnersection

    Alternatively, make siny and cosy the subjects, then square and add.
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