Math 3607: Homework 1 2021
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Math 3607: Homework 1
2021
1. (LM 2.1– 15(a): Continued square roots) Let r be defined by
r “ ffek ` dk ` ck ` bk ` ?k ` ¨ ¨ ¨
where k is any positive integer.
(a) Calculate r by hand and write down the result as an analytical formula (in terms of k).
(b) Calculate the value of r numerically for k “ 2, 3, and 4.
2. (LM 2.1–39(b): Roots of unity)
(a) Use the approach explained in the problem (the one using Euler’s formula) to find the five distinct solutions of x5 “ ´ 1 in MATLAB.
3. (Temperature conversion; adapted from LM 2.2–5.) Write a script which asks for a temperature in Fahrenheit. It should then output the temperature in degrees Celsius, kelvins,
and degree Rankine3. Then run your code with a temperature of 134˝ F.
4. (Oblate spheroid) An oblate spheroid such as the Earth is obtained by revolving an ellipse about its minor axis as shown in the figure.
Figure 1: An oblate spheroid. Image created using MATLAB.
The Earth’s equatorial radius is about 20km longer than its polar radius. The surface area of an oblate spheroid is given by
Apr1 , r2 q “ 2π ˜r 1(2) ` log ˆ ˙¸ ,
where r1 is the equatorial radius, r2 is the polar radius, and
γ “ arccos ˆ ˙ .
We assume r2 ă r1 . Write a script that inputs the equatorial and polar radii and displays both Apr1 , r2 q and the approximation 4πppr1 ` r2 q{2q2 . Apply the script to the Earth data pr1 , r2 q “ p6378.137, 6356.752q. Use format long g to display enough digits.
5. (3-D coordinate conversion) Recall that Cartesian coordinates px, y, zq in R3 are related to spherical coordinates pρ, ϕ, θq by
x “ ρ sin ϕ cos θ, y “ ρ sin ϕ sin θ, z “ ρ cos ϕ,
where ϕ P r0, πs and θ P r0, 2πq. Write a script which takes Cartesian coordinates as inputs and converts them to spherical ones. Be sure to incorporate the following convention correctly.
Convention for special cases. For points on the z-axis, that is, for points with Cartesian coordinates of the form p0, 0, zq, set r “ |z|, θ “ 0, and
$’0
’
ϕ “ &π{2 ’’%π
ifz ą 0
ifz “ 0 .
ifz ă 0
2022-06-11