cs-3333: add assignment 4

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Price Hiller 2024-11-03 13:33:38 -06:00
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#show link: set text(blue)
#set text(font: "Calibri")
#show raw: set text(font: "Fira Code")
#set table.cell(breakable: false)
#set table(stroke: (x, y) => (
left: if x > 0 {
.1pt
},
top: if y == 1 {
0.5pt
} else if y > 1 {
0.1pt
},
))
#set math.mat(delim: "[")
#set page(margin: (x: .5in, y: .5in))
#let solve(solution) = {
block(
inset: 10pt,
stroke: blue + .3pt,
fill: rgb(0, 149, 255, 15%),
radius: 4pt,
)[#solution]
}
#let solvein(solution) = {
let outset = 3pt
h(outset)
box(
outset: outset,
stroke: blue + .3pt,
fill: rgb(0, 149, 255, 15%),
radius: 4pt,
)[#solution]
}
#let note(content) = {
block(
outset: 5pt,
inset: 10pt,
stroke: luma(20%) + .3pt,
fill: luma(95%),
radius: 4pt,
)[#content]
}
#let notein(content) = {
let outset = 3pt
h(outset)
box(
outset: outset,
stroke: luma(20%) + .3pt,
fill: luma(95%),
radius: 4pt,
)[#content]
}
#align(center)[
= CS 3333 Mathematical Foundations
Homework 4 (100 points)\
#underline[Price Hiller] | #underline[zfp106]
]
#line(length: 100%, stroke: .25pt)
*Submission:*\
Same as HW1.
*Questions*\
Please write down the major intermediate steps.
1. Calculate the sum of two matrices if it is defined. (10 pts)
#enum(
numbering: "(a)",
tight: false,
number-align: start + top,
[
(5 pts)
$mat(
5, 7, -2;
6, 0, 5;
0, 4, 1;
) + mat(
3, 0, 4;
-5, -6, 8;
7, 9, 0
) =$
#note[
$mat(
5, 7, -2;
6, 0, 5;
0, 4, 1;
) + mat(
3, 0, 4;
-5, -6, 8;
7, 9, 0
) &= mat(5 + 3, 7 + 0, 4 + (-2);6 + (-5), 0 + (-6), 5 + 8; 0 + 7, 4 + 9, 1 + 0;)\
&= #solve[$mat(8, 7, 2; 1, -6, 13; 7, 13, 1;)$]$
]
],
[
(5 pts)
$mat(
2, 0, 7;
9, 5, 6;
8, 4, 0;
) + mat(
6, 1;
4, 7;
0, 5;
) =$
#solve[The addition is *not defined*. The first matrix is of order $3×3$ whereas the order of the second matrix is of order $3×2$.]
],
)
2. Calculate $A*B$ if it is defined. (25 pts)\
#enum(
numbering: "(a)",
tight: false,
number-align: start + top,
[
(5 pts) $A = 8$, $B = mat(
7, 0, -2, 4;
-6, 1, -3, 5;
)$
#note[$
"AB" &= 8 mat(
7, 0, -2, 4;
-6, 1, -3, 5;
)\
"AB" &= mat(
8 ⋅ 7, 8 ⋅ 0, 8 ⋅ -2, 8 ⋅ 4;
8 ⋅ -6, 8 ⋅ 1, 8 ⋅ -3, 8 ⋅ 5;
)\
"AB" &= #solve[$mat(
56&, 0&, -16&, 32&;
-48&, 8&, -24&, 40&;
)$]
$]
],
[
(10 pts) $A = mat(7, 0, -2, 4; -6, 1, -3, 5;)$ $B = mat(-1, 6; -4, 4; 5, 8; 0, -7;)$
#note[
$
"AB" &= mat(7, 0, -2, 4; -6, 1, -3, 5;) × mat(-1, 6; -4, 4; 5, 8; 0, -7;)\
"AB" &= mat(
((7 * -1) + (0 * -4) + (-2 * 5) + (4 * 0)), ((7 * 6) + (0 * 4) + (-2 * 8) + (4 * -7));
((-6 * -1) + (1 * -4) + (-3 * 5) + (5 * 0)), ((-6 * 6) + (1 * 4) + (-3 * 8) + (5 * -7));
)\
"AB" &= #solve[$mat(
-17&, -2&;
-13&, -91&;
)$]
$
]
],
[
(10 pts) $A = mat(1, 0, 0; 0, -1, -1; -1, 1, 0;)$ $B = mat(1, 1, -1; 0, -1, 1; 1, 1, 0;)$
#note[
$
"AB" &= mat(1, 0, 0; 0, -1, -1; -1, 1, 0;) × mat(1, 1, -1; 0, -1, 1; 1, 1, 0;)\
"AB" &= mat(
((1 * 1) + (0 * 0) + (0 * 1)), ((1 * 1) + (0 * -1) + (0 * 1)), ((1 * -1) + (0 * 1) + (0 * 0));
((0 * 1) + (-1 * 0) + (-1 * 1)), ((0 * 1) + (-1 * -1) + (-1 * 1)), ((0 * -1) + (-1 * 1) + (-1 * 0));
((-1 * 1) + (1 * 0) + (0 * 1)), ((-1 * 1) + (1 * -1) + (0 * 1)), ((-1 * -1) + (1 * 1) + (0 * 0))
)\
"AB" &= #solve[$mat(
1&, 1&, -1&;
-1, 0&, -1&;
-1, -2&, 2&
)$]\
$
]
],
)
3. Compute $"AB"$ and $"BA"$. Does $"AB" = "BA"$? (10 pts)
$A = mat(2, 2; 2, 1;)$ and $B = mat(1, 2; 1, 2;)$
#note[
$
"AB" &= mat(2, 2; 2, 1;) × mat(1, 2; 1, 2;)\
"AB" &= mat(((2 * 1) + (2 * 1)), ((2 * 2) + (2 * 2)); ((2 * 1) + (1 * 1)), ((2 * 2) + (1 * 2));)\
"AB" &= #solve[$mat(4, 8; 3, 6;)$]\
$
#align(center)[#line(length: 6cm)]
$
"BA" &= mat(1, 2; 1, 2;) × mat(2, 2; 2, 1;) \
"BA" &= mat(((1 * 2) + (2 * 2)), ((1 * 2) + (2 * 1)); ((1 * 2) + (2 * 2)), ((1 * 2) + (2 * 1));)\
"BA" &= #solve[$mat(6, 4; 6, 4;)$]\
$
#solve[$"AB" ≠ "BA"$]
]
4. Compute the transpose of matrix A (5 pts)
$A = mat(9, 2, 5; 1, 0, 4;)$
#solve[
$
A^t &= mat(9, 1; 2, 0; 5, 4)
$
]
#align(center)[#text(size: 2em)[#note[See next page]]]
5. #block(breakable: false)[Represent the following system of linear equations using matrices
$
a_11x_1 + a_12x_2 + a_13x_3 + a_14x_4 &= b_1\
a_21x_1 + a_22x_2 + a_23x_3 + a_24x_4 &= b_2\
a_31x_1 + a_32x_2 + a_33x_3 + a_34x_4 &= b_3\
a_41x_1 + a_42x_2 + a_43x_3 + a_44x_4 &= b_4
$
The representation is $A*X = B$. What is matrices $A$, $X$, and $B$? (10 pts)
#align(center)[
#solve[
#table(
stroke: (x, y) => (
left: none,
top: if y > 0 {
.5pt
},
),
columns: (auto, auto, auto, auto, auto),
align: center + horizon,
table.header([$A$], [], [$X$], [], [$B$]),
[
$
mat(
delim: "(",
a_11, a_12, a_13, a_14;
a_21, a_22, a_23, a_24;
a_31, a_32, a_33, a_34;
a_41, a_42, a_43, a_44;
)
$
],
[$⋅$],
[
$
mat(delim: "(",
x_1;
x_2;
x_3;
x_4;
)
$
],
[$=$],
[
$
mat(delim: "(",
b_1;
b_2;
b_3;
b_4;
)
$
],
)
]
]
]
6. Show the adjacency matrix for the following graph. (20 pts)
#figure(
image("./assets/graph.png", width: 60%),
) <fig-graph>
#align(center)[
#solve[
#table(
stroke: (x, y) => (
left: if y > 0 {
if x == 1 {
0.5pt
} else if x > 1 {
.1pt
}
},
top: if x > 0 {
if y == 1 {
0.5pt
} else if y > 1 {
.1pt
}
},
),
columns: (auto, auto, auto, auto, auto, auto, auto),
fill: (x, y) => {
if calc.odd(y) and y > 0 and x > 0 {
color.hsl(200deg, 60%, 40%, 25%)
} else {
none
}
},
inset: 3pt,
[ ], [A], [B], [C], [D], [E], [F],
[A], [1], [1], [0], [0], [1], [0],
[B], [1], [1], [1], [1], [1], [0],
[C], [0], [1], [1], [0], [1], [1],
[D], [0], [1], [0], [1], [1], [0],
[E], [1], [1], [1], [1], [1], [0],
[F], [0], [0], [1], [0], [0], [1],
)
#notein[
Sorry about the lack of _proper_ matrix notation. I had a hard time typesetting the row and column labels for matrices in particular in Typst :(. I have to wait on https://github.com/typst/typst/issues/445 to get resolved I guess.
#text(size: .9em)[_Arguably though, that table _is_ easier to read._]
]
]
]
#align(center)[#text(size: 2em)[#note[See next page]]]
7. #block(breakable: false)[Compute the determinant of matrix $A$. (20 pts)
$
A = mat(
6, 1, 4, 8;
4, 2, 3, 2;
4, 1, 2, 3;
9, 7, 5, 6;
)
$
#align(center)[
#note[
#align(left)[#note[
$|A| = 6mat(
2, 3, 2;
1, 2, 3;
7, 5, 6;
) - 1mat(
4, 3, 2;
4, 2, 3;
9, 5, 6;
) + 4mat(
4, 2, 2;
4, 1, 3;
9, 7, 6;
) - 8mat(
4, 2, 3;
4, 1, 2;
9, 7, 5;
)$
]]
#align(left)[#note[
#notein[The expanded values were found via *Sarrus' rule* for each $3 × 3$ matrix above.]
$
|A| &=\
6&[
(2 * 2 * 6) + (3 * 3 * 7) + (2 * 1 * 5) - (7 * 2 * 2) - (
5 * 3 * 2
) - (6 * 1 * 3)
]\
- 1&[
(4 * 2 * 6) + (3 * 3 * 9) + (2 * 4 * 5) - (9 * 2 * 2) - (
5 * 3 * 4
) - (6 * 4 * 3)
]\
+ 4&[
(4 * 1 * 6) + (2 * 3 * 9) + (2 * 4 * 7) - (9 * 1 * 2) - (
7 * 3 * 4
) - (6 * 4 * 2)
]\
- 8&[
(4 * 1 * 5) + (2 * 2 * 9) + (3 * 4 * 7) - (9 * 1 * 3) - (
7 * 2 * 4
) - (5 * 4 * 2)
]\
$
]]
#align(left)[#note[
$
|A| &=
6[21]
- 1[1]
+ 4[-16]
- 8[17]\
$
]
]
#align(center)[#solve[-75]]
]
]
]

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