Edexcel
AEA
2010
June
Q6
10 marks
Challenging +1.8
6.(a)Given that \(x ^ { 4 } + y ^ { 4 } = 1\) ,prove that \(x ^ { 2 } + y ^ { 2 }\) is a maximum when \(x = \pm y\) ,and find the maximum and minimum values of \(x ^ { 2 } + y ^ { 2 }\) .
(b)On the same diagram,sketch the curves \(C _ { 1 }\) and \(C _ { 2 }\) with equations \(x ^ { 4 } + y ^ { 4 } = 1\) and \(x ^ { 2 } + y ^ { 2 } = 1\) respectively.
(c)Write down the equation of the circle \(C _ { 3 }\) ,centre the origin,which touches the curve \(C _ { 1 }\) at the points where \(x = \pm y\) .
Edexcel
AEA
2016
June
Q3
9 marks
Challenging +1.2
3.The points \(A , B , C , D\) and \(E\) are five of the vertices of a rectangular cuboid and \(A E\) is a diagonal of the cuboid.With respect to a fixed origin \(O\) ,the position vectors of \(A , B , C\) and \(D\) are \(\mathbf { a , b , c }\) and \(\mathbf{d}\) respectively,where
$$\mathbf { a } = \left( \begin{array} { c }
1 \\
2 \\
- 1
\end{array} \right) , \quad \mathbf { b } = \left( \begin{array} { c }
0 \\
- 3 \\
- 8
\end{array} \right) , \quad \mathbf { c } = \left( \begin{array} { c }
4 \\
- 1 \\
- 10
\end{array} \right)$$