OCR MEI Paper 3 2020 November — Question 5

Exam BoardOCR MEI
ModulePaper 3 (Paper 3)
Year2020
SessionNovember
TopicReciprocal Trig & Identities

5 Fig. 5 shows part of the curve \(y = \operatorname { cosec } x\) together with the \(x\) - and \(y\)-axes. \begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{a13f7a05-e2d3-4354-a0c7-ef7283eff514-06_732_625_317_244} \captionsetup{labelformat=empty} \caption{Fig. 5}
\end{figure}
  1. For the section of the curve which is shown in Fig. 5, write down
    1. the equations of the two vertical asymptotes,
    2. the coordinates of the minimum point.
  2. Show that the equation \(x = \operatorname { cosec } x\) has a root which lies between \(x = 1\) and \(x = 2\).
  3. Use the iteration \(\mathrm { x } _ { \mathrm { n } + 1 } = \operatorname { cosec } \left( \mathrm { x } _ { \mathrm { n } } \right)\), with \(x _ { 0 } = 1\), to find
    1. the values of \(x _ { 1 }\) and \(x _ { 2 }\), correct to 5 decimal places,
    2. this root of the equation, correct to 3 decimal places.
  4. There is another root of \(x = \operatorname { cosec } x\) which lies between \(x = 2\) and \(x = 3\). Determine whether the iteration \(\mathrm { x } _ { \mathrm { n } + 1 } = \operatorname { cosec } \left( \mathrm { x } _ { \mathrm { n } } \right)\) with \(x _ { 0 } = 2.5\) converges to this root.
  5. Sketch the staircase or cobweb diagram for the iteration, starting with \(x _ { 0 } = 2.5\), on the diagram in the Printed Answer Booklet.