MAST10006 Calculus 2 Summer Semester Assessment, 2020
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Summer Semester Assessment, 2020
School of Mathematics and Statistics
MAST10006 Calculus 2
Question 1 (10 marks)
In this question you must state if you use standard limits, continuity, l’Hˆopital’s rule, the sandwich theorem or any tests for convergence of series; you do not need to state if you use any limit laws.
Let f : R → R be given by
'
f(x) =〈'
(
北 − 北2 ,
kx,
cosec (2(π北)) log x,
x < 0
0 ≤ x ≤ 1
x > 1
where k ∈ R is a constant.
(a) Find lim f(x), or explain why it does not exist.
北→0
(b) For which value(s) of k is f continuous at x = 1? Show all your working.
Question 2 (14 marks)
In this question you must state if you use standard limits, continuity, l’Hˆopital’s rule, the sandwich theorem or any tests for convergence of series; you do not need to state if you use any limit laws.
Let
4n
n3 + r2n ,
where r ∈ R is a constant.
(a) If r = 2 then does the sequence {an} converge or diverge? Justify your answer.
∞
(b) If r = 2 then does the series 工 an converge or diverge? Justify your answer.
n=1
(c) If r = 3 then does the sequence {an} converge or diverge? Justify your answer.
∞
(d) If r = 3 then does the series 工 an converge or diverge? Justify your answer. n=1
(e) For which value(s) of r does the sequence {an} converge?
∞
(f) For which value(s) of r does the series 工 an converge?
n=1
Question
Evaluate
Question 4 (12 marks)
Evaluate the following integrals:
(a) \ x5 ^1 − x2 dx
(b) \ dx
Question 5 (12 marks)
(a) Find the general solution y(x) of
= x (e北2 − 2y) .
(b) Make the substitution z = x + y and reduce
dx = (x + y)2 log (x2 + 1) − 1
to the differential equation
dz
Then find the general solution y(x) of equation (1).
Question 6 (10 marks)
Suppose that the population p = p(t) of a new type of coronavirus in a patient’s body satisfies
= (1 − ) − h, (t ≥ 0) (2)
where h ≥ 0 is a constant depending on the drug used in the medical treatment to kill the virus.
(a) Determine the value(s) of h for which there is exactly one equilibrium solution of equa-
tion (2).
(b) For each value of h that you find in part (a) determine the equilibrium solution and its
stability.
(c) Determine the value(s) of h for which p(t) strictly decreases with t irrespective of the initial population.
(d) Given h = 0 and p(0) = 1314, does p(t) have any inflection point for t ≥ 0; if so, find the population when inflection first occurs. Explain why.
(e) Given h = 0 and p(0) = 520, does p(t) have any inflection point for t ≥ 0; if so, find the
population when inflection first occurs. Explain why.
Question 7 (12 marks)
(a) Find the solution of the differential equation
y\\ + 2y\ + y = 25sin(2北)
subject to the boundary conditions y(0) = −4, y(π) = π − 4.
(b) Find the general solution of the differential equation
y\\ + y\ − 2y = sinh 北.
Question 8 (6 marks)
Consider the differential equation
− 8m + 25m2y = 0
where m ∈ R is a constant.
(a) Determine the value(s) of m for which y = e −4北 sin(3北) is a solution of equation (3). (b) For each value of m that you find in part (a) find the general solution of equation (3).
(c) Determine the value(s) of m for which lim y(北) = 0 for every solution y = y(北) of 北→∞
equation (3).
Question 9 (7 marks)
Let S be a surface in R3 given by z = cosh ^x2 + y2 for (x,y) ∈ R2 .
(a) Find an expression for the level curve of this surface when z = c. For what value(s) of c
does the level curve exist?
(b) Sketch the cross section of the surface in the yz plane. Label each axis intercept with its
value.
(c) Sketch the surface S in R3 . Label each axis intercept with its value.
Question 10 (15 marks)
Let f : R2 → R, f(x,y) = 3x2 − 2x3 − 3y2 + 6xy .
(a) Find the gradient of f .
(b) Find the directional derivative of f at (0, 1) in the direction from (0, 1) towards (1, 0).
(c) Find the equation of the tangent plane to the surface z = f(x,y) at the point where (x,y) = (0, 1).
(d) Find the second order partial derivatives f北北 , fyy , f北y and fy北 of f .
(e) Find all stationary points of f, and classify each point as a local maximum, local minimum
or saddle point.
(f) Evaluate \−2(1) \0 2 f(x,y)dxdy .
2023-02-15