2024 TWO(a)

Achievement
Question
A function is defined parametrically by the pair of equations:

x=3t2+1x = 3t^2 + 1 and y=cost.y = \cos t.

Find an expression for dydx\frac{\mathrm{d}y}{\mathrm{d}x}.
Official Answer
dxdt=6t\dfrac{dx}{dt}=6t

dydt=sint\dfrac{dy}{dt}=-\sin t

dydx=sint6t\dfrac{dy}{dx}=\dfrac{-\sin t}{6t}
Grading Criteria

Achievement (u)

  • Correct expression for dydx\dfrac{dy}{dx}.
  • dydx\dfrac{dy}{dx} can be expressed in term of x,yx,y.

Merit (r)

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Excellence T1

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Excellence T2

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Video Explanation
2024 NCEA L3 Calculus Exam Walkthrough by infinityplusone(starts at 20:02)
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