2023 CJC Promo Q11

2023 CJC Promo Q11

15 marks
Promo

A curve \(C\) has parametric equations

\(x=1-2{{t}^{2}}\), \(\qquad\) \(y={{t}^{3}}+1\), \(\qquad\) for \(t\in \mathbb{R}\).

  1. Sketch \(C\), indicating the coordinates of the points of intersection with the axes.[3]

The line \(x+y=2\) cuts \(C\) at the points \(A\) and \(B\) where the \(x\)-coordinate of \(A\) is greater than the \(x\)-coordinate of \(B\).

  1. Find the exact length of \(AB\) in the form \(k\sqrt{2}\) where \(k\) is an integer to be determined.[3]
  2. The point \(M\) is the midpoint of \(AP\) where \(P\) is the point \(\left( 1-2{{p}^{2}},{{p}^{3}}+1 \right)\). Find a cartesian equation of the curve traced by \(M\) as \(p\) varies. Leave your answer in the form \({{\left( ax+b \right)}^{3}}={{\left( cy+d \right)}^{2}}\), where \(a\), \(b\), \(c\) and \(d\) are integers to be determined.[3]
    \(y=\left[ \mathrm{f}\left( p \right) \right]x+{{p}^{3}}+\frac{8p}{3}+1-\frac{4}{3p}\)
    Where \(\mathrm{f}\left( p \right)\) is an expression in \(p\) to be determined.[3]
  3. Show that the equation of the normal to \(C\) at the point \(P\) is
  4. Find the acute angle between the normals to the curve at \(x=-7\).[3]

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Answer:(b) \(8\sqrt{2}\) (b) \({{\left( 1-x \right)}^{3}}={{\left( 2y-2 \right)}^{2}}\) (e) \({{67.4}^{\circ }}\) or \(1.18\) rad

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