Date | May 2021 | Marks available | 2 | Reference code | 21M.2.AHL.TZ2.7 |
Level | Additional Higher Level | Paper | Paper 2 | Time zone | Time zone 2 |
Command term | Determine | Question number | 7 | Adapted from | N/A |
Question
Consider the following system of coupled differential equations.
Find the value of
Find the eigenvalues and corresponding eigenvectors of the matrix .
Hence, write down the general solution of the system.
Determine, with justification, whether the equilibrium point is stable or unstable.
(i) at .
(ii) at .
Sketch a phase portrait for the general solution to the system of coupled differential equations for , .
Markscheme
(M1)
(A1)
OR A1
(M1)
Note: This M1 can be awarded for attempting to find either eigenvector.
possible eigenvector is (or any real multiple) A1
possible eigenvector is (or any real multiple) A1
[6 marks]
(M1)A1
Note: Award M1A1 for , M1A0 if LHS is missing or incorrect.
[2 marks]
two (distinct) real negative eigenvalues R1
(or equivalent (eg both as ))
⇒ stable equilibrium point A1
Note: Do not award R0A1.
[2 marks]
(M1)
(i) A1
(ii) A1
[3 marks]
A1A1A1A1
Note: Award A1 for a phase plane, with correct axes (condone omission of labels) and at least three non-overlapping trajectories. Award A1 for all trajectories leading to a stable node at . Award A1 for showing gradient is negative at and . Award A1 for both eigenvectors on diagram.
[4 marks]