Edexcel AEA 2022 June — Question 6 24 marks

Exam BoardEdexcel
ModuleAEA (Advanced Extension Award)
Year2022
SessionJune
Marks24
PaperDownload PDF ↗
TopicSequences and Series
TypeInfinite Products and Nested Sequences
DifficultyHard +2.3 This AEA question requires tracking geometric sequences across multiple iterations, finding limits of infinite series, working with nested constructions, and applying the pattern to a different geometry. It demands sustained multi-step reasoning, pattern recognition, and careful algebraic manipulation across seven interconnected parts, placing it well above typical A-level but not at the absolute extreme of AEA difficulty.
Spec1.04i Geometric sequences: nth term and finite series sum1.04j Sum to infinity: convergent geometric series |r|<11.08g Integration as limit of sum: Riemann sums

6. \begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{71cd126f-1c7d-4e37-a26d-7ff98a74fd79-22_481_1139_189_463} \captionsetup{labelformat=empty} \caption{Figure 2}
\end{figure} Figure 2 shows the first few iterations in the construction of a curve, \(L\).
Starting with a straight line \(L _ { 0 }\) of length 4 , the middle half of this line is replaced by three sides of a trapezium above \(L _ { 0 }\) as shown, such that the length of each of these sides is \(\frac { 1 } { 4 }\) of the length of \(L _ { 0 }\) After the first iteration each line segment has length one.
In subsequent iterations, each line segment parallel to \(L _ { 0 }\) similarly has its middle half replaced by three sides of a trapezium above that line segment, with each side \(\frac { 1 } { 4 }\) the length of that line segment. Line segments in \(L _ { n }\) are either parallel to \(L _ { 0 }\) or are sloped.
  1. Show that the length of \(L _ { 2 }\) is \(\frac { 23 } { 4 }\)
  2. Write down the number of
    1. line segments in \(L _ { n }\) that are parallel to \(L _ { 0 }\)
    2. sloped line segments in \(L _ { 2 }\) that are not in \(L _ { 1 }\)
    3. new sloped line segments that are created by the ( \(n + 1\) )th iteration.
  3. Hence find the length of \(L _ { n }\) as \(n \rightarrow \infty\) The area enclosed between \(L _ { 0 }\) and \(L _ { n }\) is \(A _ { n }\)
  4. Find the value of \(A _ { 1 }\)
  5. Find, in terms of \(n\), an expression for \(A _ { n + 1 } - A _ { n }\)
  6. Hence find the value of \(A _ { n }\) as \(n \rightarrow \infty\) The same construction as described above is applied externally to the three sides of an equilateral triangle of side length \(a\).
    Given that the limit of the area of the resulting shape is \(26 \sqrt { 3 }\)
  7. find the value of \(a\).

6.

\begin{figure}[h]
\begin{center}
  \includegraphics[alt={},max width=\textwidth]{71cd126f-1c7d-4e37-a26d-7ff98a74fd79-22_481_1139_189_463}
\captionsetup{labelformat=empty}
\caption{Figure 2}
\end{center}
\end{figure}

Figure 2 shows the first few iterations in the construction of a curve, $L$.\\
Starting with a straight line $L _ { 0 }$ of length 4 , the middle half of this line is replaced by three sides of a trapezium above $L _ { 0 }$ as shown, such that the length of each of these sides is $\frac { 1 } { 4 }$ of the length of $L _ { 0 }$

After the first iteration each line segment has length one.\\
In subsequent iterations, each line segment parallel to $L _ { 0 }$ similarly has its middle half replaced by three sides of a trapezium above that line segment, with each side $\frac { 1 } { 4 }$ the length of that line segment.

Line segments in $L _ { n }$ are either parallel to $L _ { 0 }$ or are sloped.
\begin{enumerate}[label=(\alph*)]
\item Show that the length of $L _ { 2 }$ is $\frac { 23 } { 4 }$
\item Write down the number of
\begin{enumerate}[label=(\roman*)]
\item line segments in $L _ { n }$ that are parallel to $L _ { 0 }$
\item sloped line segments in $L _ { 2 }$ that are not in $L _ { 1 }$
\item new sloped line segments that are created by the ( $n + 1$ )th iteration.
\end{enumerate}\item Hence find the length of $L _ { n }$ as $n \rightarrow \infty$

The area enclosed between $L _ { 0 }$ and $L _ { n }$ is $A _ { n }$
\item Find the value of $A _ { 1 }$
\item Find, in terms of $n$, an expression for $A _ { n + 1 } - A _ { n }$
\item Hence find the value of $A _ { n }$ as $n \rightarrow \infty$

The same construction as described above is applied externally to the three sides of an equilateral triangle of side length $a$.\\
Given that the limit of the area of the resulting shape is $26 \sqrt { 3 }$
\item find the value of $a$.
\end{enumerate}

\hfill \mbox{\textit{Edexcel AEA 2022 Q6 [24]}}