MAST20029 Engineering Mathematics 2022
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Semester 1 Sample Mid Semester Test, 2022
School of Mathematics and Statistics
MAST20029 Engineering Mathematics
Question 1 (6 marks)
Consider the double integral
2 3
sinh(y2 ) dyd北.
′ 3x
(a) Sketch the region of integration.
(b) By changing the order of integration, evaluate the double integral.
Question 2 (7 marks)
Determine the surface area of the part of the surface z = xy that lies inside the cylinder given by x2 + y2 = 1 .
Question 3 (8 marks)
Let F(x, y, X) = (sin y cos x)i + (sin x cos y)j + e2z k.
(a) Show that F is a conservative vector field.
(b) Find a scalar function φ such that F = Vφ .
(c) Let C be the boundary of the square with vertices (0, 0), (1, 0), (1, 1), (0, 1), in the x-y plane. Determine the work done by F in moving a particle in an anticlockwise direction around C.
Question 4 (10 marks)
Consider the surface S of the solid region V formed by the cylinder 北2 + y2 - 4 which lies between the planes z = 1 and z = 4. Let S be oriented with an outward unit normal.
Use Gauss’ Theorem to determine the flux of the vector field
F(北, y, z) = ╱北3 i + y3j + z3 k、
across S.
Question 5 (9 marks)
Consider the following system of differential equations
dx dy
dt dt
with general solution
┌ y(x) ┐ = α 2 ┌ 1-1 ┐ e-t + α2 ┌ 1-2 ┐ e-3t
Sketch the phase portrait near the critical point at the origin. To sketch the phase portrait, determine:
< any special cases of the orbits,
< how the orbits behave as t o -o,
< how the orbits behave as t o o,
< the slope of the orbits when x = 0,
< the slope of the orbits when y = 0.
In your sketch, show all the straight line orbits and at least four general orbits.
MAST20029 Engineering Mathematics Formulae Sheet 1) Change of Variable of Integration in 2D
f (x, y) dxdy = f (x(u, v), y(u, v))lJ (u, v)l dudv
R R*
2) Transformation to Polar Coordinates
x = r cos θ, y = r sin θ, J (r, θ) = r
3) Change of Variable of Integration in 3D
f (x, y, z) dxdydz = F (u, v, w)lJ (u, v, w)l dudvdw
V V *
4) Transformation to Cylindrical Coordinates
x = r cos θ, y = r sin θ, z = z, J (r, θ, z) = r
5) Transformation to Spherical Coordinates
x = r cos θ sin φ, y = r sin θ sin φ, z = r cos φ, J (r, θ, φ) = r2 sin φ
6) Line Integrals
f (x, y, z) ds =
C
b
f (x(t), y(t), z(t)) ^x\ (t)2 + y\ (t)2 + z\ (t)2 dt
a
7) Work Integrals
F(x, y, z) . dr =
C
8) Surface Integrals
b dx dy dz
a dt dt dt
g(x, y, f (x, y))′fx(2) + fy(2) + 1 dxdy
9) Flux Integrals For a surface with upward unit normal,
-F2fx - F2fy + F3 dydx
R
10) Gauss’ (Divergence) Theorem
V . F dV = F . nˆ dS
V S
11) Stokes’ Theorem
(V O F) . nˆ dS = F . dr
S C
12) Complex Exponential Formulae
sinh x = (ex - e-x )
sin z = ╱eiz - e-iz、
13) Standard Integrals
sec x dx = logel sec x + tan xl + C cosec x dx = logel cosec x - cot xl + C
sec2 x dx = tan x + C cosec2 x dx = - cot x + C
sinh x dx = cosh x + C cosh x dx = sinh x + C
sech2 x dx = tanh x + C cosech2 x dx = - coth x + C
dx = arcsin ╱ 、+ C dx = arcsinh ╱ 、+ C
dx = arccos ╱ 、+ C dx = arccosh ╱ 、+ C
dx = arctan ╱ 、+ C dx = arctanh ╱ 、+ C
where a > 0 is constant and C is an arbitrary constant of integration.
14) Trigonometric and Hyperbolic Formulae
cos2 x + sin2 x = 1
1 + tan2 x = sec2 x
cot2 x + 1 = cosec2 x
cos(2x) = cos2 x - sin2 x
cos(2x) = 2 cos2 x - 1
cos(2x) = 1 - 2 sin2 x
sin(2x) = 2 sinx cos x
sin(x + y) = sin x cos y + cos x sin y
cos(x + y) = cos x cos y - sin x sin y
sin x sin y = [cos(x - y) - cos(x + y)]
cos x cos y = [cos(x - y) + cos(x + y)]
sin x cos y = [sin(x - y) + sin(x + y)]
2022-09-04