Duration: 3 hours Marks: 100
Examiners:
First: Ms LE Greyling
Second: Mr S Blose
External: Dr JN Mwambakana
Use of a non-programmable pocket calculator is permissible.
This is a closed book examination and will be IRIS invigilated.
This online paper is the property of UNISA and may not be distributed electronically.
This examination question paper consists of 3 pages including this cover page plus
Formulae sheets (pages 4 to 8) plus
A table of integrals (pages 9 and 10) plus
A table of Laplace transforms (page 11).
Examination rules:
1. Students must upload their answer scripts in a single PDF file (answer scripts must not be password
protected or uploaded as “read only” files).
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, -2- MAT3700
September-December 2020
QUESTION 1
Solve the following differential equations:
1.1 1 x dy
2
dx
1 y . 2
(4)
1.2 x 2
y 2 dx x 2 xy dy 0 Hint: Let y vx . (7)
dy
1.3 y cot x cos x. (7)
dx
[18]
QUESTION 2
Find the general solution of the following differential equation using the method of
d 2y dy
undetermined coefficients: 3 2 2 y 2x 3 . (10)
dx dx
[10]
QUESTION 3
Find the general solution of the following differential equations using D-operator methods:
3.1 D 2
3D 2 y sin3 x . (8)
3.2 D 2
6D 9 y e 2 x
cosh 2 x . (6)
[14]
QUESTION 4
Solve for x and y by using D-operator methods in the following set of simultaneous
equations:
D 1 y x 4et
. (10)
y D 3 x 1
[10]
QUESTION 5
Determine the following:
5.1
L et cos 2t . (2)
8se 2s
5.2 L1 2 . (4)
s 9
[6]
[TURN OVER]
, -3- MAT3700
September-December 2020
QUESTION 6
Given y " y sin t
Use Laplace transforms to solve the equation if the initial values for the equation are
y 0 1 and y ' 0 0 . (8)
[8]
QUESTION 7
The equation of motion of a system is
d 2x dx
2
5 4 x 3 t 2
dt dt
If x 0 2 and x ' 0 2 find an expression for the displacement x in terms of t.
(12)
[12]
QUESTION 8
2
The period, T, of natural vibrations of a building is given by T where is an
2 1
eigenvalue of matrix A . Find the period(s) if A . (5)
1 2
[5]
QUESTION 9
Find all the eigenvalues of matrix A and an eigenvector corresponding to .
2 0 0
A 4 1 0 . (7)
1 2 1
[7]
QUESTION 10
A function f(x) is defined by
2 x 0
f x .
0x2
Determine the Fourier series expansion of the periodic function f(x) with period 4.
(10)
[10]
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