MATH1055 Numbers and Vectors Semester One 201819
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MATH1055
Numbers and Vectors
Semester One 201819
SECTION A
A1. Use mathematical induction to prove that the sum of the irst N odd natural numbers is equal to N2 , that is
1 + 3 + 5 + · · · + (2N − 1) = N2 ,
for all natural numbers N .
A2. Write the complex number
z = 2e2iT/3 − e —iT/3
in exponential form.
A3. Sketch the set in the complex plane
M = {z ∈ C : |Re(z)| < 1, |z| > 1}.
A4. Is the sequence (an ) deined by an = 2019n /2018n for n ≥ 1 bounded (bounded above, bounded below)? Is it convergent? Is it decreasing or increasing?
2n2 + 1
n→∞ n2 − 1 10 + 3n5 .
A6. When is an ininite series called absolutely convergent? What can you say about the convergence of an absolutely convergent ininite series?
A7 . Find the equation for the sphere with centre at C = (3, −2, 1) and passing through the
point P = (1, − 1, 5) .
A8. Compute the vector product of a = (3, 1, 0) and b = (1, − 1, −3) and ind a unit vector
SECTION B
B1. (a) Deine the modulus |z| and argument arg(z) of the complex number z = x + iy . Write the modulus and argument of the ratio z/w of two complex numbers in terms of arg(z), |z|, arg(w) and |w|.
(b) Find two complex numbers z and w such that
zw = 3 + i^3, arg(z) = −T/6, |w| = 1.
(c) Sketch the set M deined by
M = {z ∈ C : Im(z) < 1, T/4 < arg(z) < 3T/4}.
(d) State Euler’s formula and use it to derive the double-angle formulae for the sine and cosine.
(e) Find all complex roots of the equation
z6 − 1 − i = 0.
B2. (a) Consider the ininite series
∞
工 qk ,
k=0
where q ∈ R.
Show – using induction or otherwise – that for the partial sums sn = 之k(n)=0 qk , we have
1 − q .
(b) Discuss the convergence of the series 之 qk in its dependence on q . Determine its sum for the values of q such that the series converges.
(c) Geometric series can be used to obtain expressions for rational numbers, given in
decimal form, as the ratio of two coprime integers.
For x = 0.123123123 · · · = 0.123 we can also write
x = 123/1000 + 123/1000000 + 123/1000000000 + ...
Use this to express x as the ratio of two coprime integers.
(d) For x ∈ R, a function f is deined as an ininite series
∞
f(x) =工 (3^3x)k . k=0
Using the ratio test or otherwise, show that the series converges for − 1/27 < x <
(e) Determine f(x) (i.e., the value of the sum) for − 1/27 < x < 1/27.
B3 . Consider the plane S given by x − 2y + 3z = 5, the line L given by (1 − 3t,2 + t,4 + t) ,
t ∈ R, and the point P = (1, 4, −3) .
(a) Find the coordinates of the intersection point Q of S and L. (b) Find the coordinate equation of the plane T containing P and L.
(c) Compute the cosine of the angle between the planes S and T .
(d) The line through P orthogonal to the plane S intersects S in the point R. Find R and compute the distance from P to S .
(e) Obtain the equation of the sphere with centre P which touches the plane S .
2022-08-04