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  1. O

    Find the locus of a point question

    You have found the parametric coordinates of N. ie N(ap,0). Since there is no parameter in the y-coordinate (since y = 0, a constant), this is the locus of N. This is because no value of p can alter the y value. So the locus of N is y = 0. (Note: usually when this situation occurs, you...
  2. O

    Past HSC Q8.

    That's a really nice method damo but KFunk, there's nothing wrong with yours. In fact, judging by the first two parts to the question, it's probably the way they wanted you to approach it. It's not that messy either, considering it's a Q8.
  3. O

    conical pendulum (easy type)

    Hmm, I got the same answer as robbo, except with a pi<sup>2</sup> in the denominator... Ah well robbo, that's 119/120 :)
  4. O

    Prob

    I'll give it a shot....(no pun intended :) ) P(Pat winning) = P(win in 3 sets) + P(win in 4 sets) + P(win in 5 sets) ........................= (2/3)<sup>3</sup> + (2/3)*<sup>3</sup>C<sub>1</sub>*(2/3)<sup>2</sup>*(1/3) + (2/3)*<sup>4</sup>C<sub>2</sub>*(2/3)<sup>2</sup>*(1/3)<sup>2</sup>...
  5. O

    CSSA Results

    Yes, and how did you get it please?
  6. O

    Cssa Trials...

    Yeah, most people do the dry cell, so that question didn't help me very much at all. Now that I think of it though, I probably could've deduced the correct answer had I spent more time on it.
  7. O

    Cssa Trials...

    Hmm, what about the dry cell question in the multiple choice? Not very handy if you've studied the lead-acid cell. I was certain the syllabus only requires you to know one of the two, and not one in particular. Ah well...
  8. O

    question

    Let f(x) = x^3 - 12x^2 + 45x then find the stationary points of y = f(x). Then work out how far you can bring down the graph so that the stationary points are on opposite sides of the x-axis (ie 3 distinct roots). This will give you the values of m.
  9. O

    2001 moriah solutions

    Thanks for that. I did that test a while ago and have been looking for the solutions to it. Just a query regarding Q4 iv) (the locus question). Shouldn't you specify the restrictions of the locus? Obviously it can only exist between the y-axis and the right branch of the hyperbola, so...
  10. O

    mechanics plz help.

    There are two forces acting on the particle: 1) weight downwards = mg 2) resistance upwards = 0.1mv<sup>2</sup> Therefore, F = ma = mg - 0.1mv<sup>2</sup> giving the equation of motion: a = g - 0.1v<sup>2</sup> Now, terminal velocity, U, is approached as a --> 0 So...
  11. O

    Couple of Complex Quickies

    1)ii) RTP: (1+sinz+icosz)^5+i(1+sinz-icosz)^5=0 (1+sinz+icosz)^5= -i(1+sinz-icosz)^5 (1+sinz+icosz)^5/(1+sinz-icosz)^5 = -i [(1+sinz+icosz)/(1+sinz-icosz)]^5 = -i LHS = (sinz+icosz)^5 {from i} .......= sin(pi) + icos(pi) .......= -i .......= RHS 2b) The locus in a) is a...
  12. O

    harder projectiles

    It took me a while to get it but I'll quickly list the steps I took... 1) Use the fact that max height = 2h to find an expression for h in terms of V, @ and g. 2) Use the quadratic formula to find the 2 values of t when y = h. 3) Use x = Vtcos@ and sub the previous values of t to find...
  13. O

    all time classic R&B and soul songs - add to list

    The R. Kelly ones that I think of straight away.... - If I Could Turn Back The Hands Of Time - I Wish - Heaven I Need A Hug - I'm Your Angel (with Celine Dion) - What I Feel/Issues
  14. O

    Seinfeld

    1) Who was your favourite character? Why? George, I just love the unfortunate circumstances he gets himself into... 2) Who did you least like? Why? Lloyd Braun - I just hate that smile, haha. 3) What's your favourite quote? George to unknown attractive woman: "Hey, my name's George, I'm...
  15. O

    1/2 yearly question marked wrong.....i swear im right....

    Hmm, what if |x/a| > 1? The inverse sine is not defined for this.
  16. O

    Quick question.

    Hold on, If a >= b, how can you say that this implies a > b, considering the case when a = b?
  17. O

    Putting an absolute value sign around a log?

    Regarding log functions in definite integrals, you can actually prove that ln(-x) will produce the same result as ln(x). However, this requires knowledge of Euler's formula and that's why absolute values are more encouraged in 4u.
  18. O

    quick question (complex numbers)

    Your algebraic reasoning is still correct. Just square both sides and you get the result.
  19. O

    I'm missing something here (Integration q)

    you could probably do it by inspection, noticing that the derivative of secx is secxtanx
  20. O

    Polynomials Question

    Yeah, I've seen the solution to this question and it involves coming up with a lot of identities and manipulating them to get the answer. Agreed.
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