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Overview
Fun math puzzles based on the Twelve Labors of Hercules
How might Hercules, the most famous of the Greek heroes, have used mathematics to complete his astonishing Twelve Labors? From conquering the Nemean Lion and cleaning out the Augean Stables, to capturing the Erymanthean Boar and entering the Underworld to defeat the three-headed dog Cerberus, Hercules and his legend are the inspiration for this book of fun and original math puzzles.
While Hercules relied on superhuman strength to accomplish the Twelve Labors, Mythematics shows how math could have helped during his quest. How does Hercules defeat the Lernean Hydra and stop its heads from multiplying? Can Hercules clean the Augean Stables in a day? What is the probability that the Cretan Bull will attack the citizens of Marathon? How does Hercules deal with the terrifying Kraken? Michael Huber's inventive math problems are accompanied by short descriptions of the Twelve Labors, taken from the writings of Apollodorus, who chronicled the life of Hercules two thousand years ago. Tasks are approached from a mathematical modeling viewpoint, requiring varying levels of knowledge, from basic logic and geometry to differential and integral calculus. Mythematics provides helpful hints and complete solutions, and the appendixes include a brief history of the Hercules tale, a review of mathematics and equations, and a guide to the various disciplines of math used throughout the book.
An engaging combination of ancient mythology and modern mathematics, Mythematics will enlighten and delight mathematics and classics enthusiasts alike.
Product Details
| ISBN-13: | 9781400831906 |
|---|---|
| Publisher: | Princeton University Press |
| Publication date: | 09/08/2009 |
| Sold by: | Barnes & Noble |
| Format: | eBook |
| Pages: | 216 |
| File size: | 2 MB |
About the Author
Read an Excerpt
Mythematics
SOLVING THE TWELVE LABORS OF HERCULESBy Michael Huber
Princeton University Press
Copyright © 2009 Princeton University PressAll right reserved.
ISBN: 978-0-691-13575-5
Chapter One
The First Labor: The Nemean Lion
From Apollodorus:
First, Eurystheus ordered him to bring the skin of the Nemean lion; now that was an invulnerable beast begotten by Typhon. On his way to attack the lion he came to Cleonae and lodged at the house of a day-laborer, Molorchus; and when his host would have offered a victim in sacrifice, Hercules told him to wait for thirty days, and then, if he had returned safe from the hunt, to sacrifice to Saviour Zeus, but if he were dead, to sacrifice to him as to a hero. And having come to Nemea and tracked the lion, he first shot an arrow at him, but when he perceived that the beast was invulnerable, he heaved up his club and made after him. And when the lion took refuge in a cave with two mouths, Hercules built up the one entrance and came in upon the beast through the other, and putting his arm round its neck held it tight till he had choked it; so laying it on his shoulders he carried it to Cleonae. And finding Molorchus on the last of the thirty days about to sacrifice the victim to him as to a dead man, he sacrificed to Saviour Zeus and brought the lion to Mycenae. Amazed at his manhood, Eurystheus forbade him thenceforth to enter the city, but ordered him to exhibit the fruits of his labours before the gates. They say, too, that in his fear he had a bronze jar made for himself to hide in under the earth, and that he sent his commands for the labours through a herald, Copreus, son of Pelops the Elean. This Copreus had killed Iphitus and fled to Mycenae, where he was purified by Eurystheus and took up his abode.
1.1. The Tasks
The Nemean lion was ravaging the countryside near the town of Nemea, which is northwest of Mycenae. Hercules has three tasks to complete. After he tracks the lion, he shoots an arrow at the beast. First, he determines the speed at which his arrow strikes the invulnerable lion, given an angle of elevation and a distance to the lion (the Shooting an Arrow problem). In the second task, Hercules determines which set of regular polygons will allow him to tile the area of the cave mouth and trap the lion inside the cave (the Closing the Cave Mouth problem). As an associated exercise, Hercules chooses the mouth of the cave which will give him the greatest chance of finding the lion (the Zeus Makes a Deal problem).
1.1.1. Shooting an Arrow
Task: Calculate the speed at which an arrow strikes the lion at a distance of 200 meters given a launch angle of 20?. Assume Hercules aims for the lion's head and shoulder area, which is the same distance off the ground as the arrow when it leaves Hercules' bow. Ignoring air resistance, how long does it take the arrow to travel from Hercules' bow to the lion?
1.1.2. Hercules Closes the Cave Mouth
Task: To defeat the lion, Hercules must close up one cave entrance and attack the lion through the other. He finds several stacks of tiles nearby, each of which contains sets of regular polygons. There is one stack of equilateral triangles, one stack of squares, one stack of regular pentagons, one stack of regular hexagons, and one stack of regular octagons. Which stack(s) of polygons will allow Hercules to construct an edge-to-edge tiling in order to close up the mouth of the cave with no two tiles overlapping?
1.1.3. Exercise: Zeus Makes a Deal
Task: Suppose that the cave has three, rather than two, mouths and that the lion is hiding just inside one of the mouths. Hercules selects one of the three cave mouths at random and is about to enter when Zeus, the king of the gods, suddenly tells him that the lion is not in a second cave mouth (not the one Hercules has choosen). Should Hercules change his mind and enter the remaining third mouth to the cave?
1.2. The Solutions
1.2.1. Shooting an Arrow
From Apollodorus:
First, Eurystheus ordered him to bring the skin of the Nemean lion; now that was an invulnerable beast begotten by Typhon. On his way to attack the lion he came to Cleonae and lodged at the house of a day-laborer, Molorchus; and when his host would have offered a victim in sacrifice, Hercules told him to wait for thirty days, and then, if he had returned safe from the hunt, to sacrifice to Saviour Zeus, but if he were dead, to sacrifice to him as to a hero. And having come to Nemea and tracked the lion, he first shot an arrow at him.
Task: Calculate the speed at which an arrow strikes the lion at a distance of 200 meters given a launch angle of 20?. Assume Hercules aims for the lion's head and shoulder area, which is the same distance off the ground as the arrow when it leaves Hercules' bow. Ignoring air resistance, how long does it take the arrow to travel from Hercules' bow to the lion?
Solution: Let's place a coordinate axis system so that the point where the arrow leaves Hercules' bow is at the origin when time t = 0. It is natural to assume constant acceleration and let the positive y-axis be vertically upward. The constant acceleration, directed only downward, is due to gravity and is denoted by -g. Further, think of this as a two-dimensional motion of the arrow through the air. We will neglect any effects the air might have on the arrow (in a simplified model, Hercules can neglect any effects of wind on the arrow's time of flight).
Because of our reference system, the initial position is given by x(0) = y(0) = 0. The initial velocity at time t = 0, which is at the exact instant the arrow begins its flight, is given by [upsilon](0) = [[upsilon].sub.0]. With constant acceleration, we obtain the velocity by multiplying the acceleration by time t and adding the initial velocity:
[upsilon](t) = -gt + [[upsilon].sub.0]. (1.1)
Using trigonometry (see Figure 1.1), we can then determine the initial x- and y-components of [[upsilon].sub.0] as
[[upsilon].sub.x0] = [[upsilon].sub.0] cos [theta] and [[upsilon].sub.y0] = [[upsilon].sub.0] sin [theta].
Since there is no acceleration in the x-direction, the horizontal component of velocity will remain constant. What does this mean? The horizontal velocity component ([[upsilon].sub.0] cos [theta]) will keep its initial value throughout the flight of the arrow. The vertical component, however, will change because of the downward acceleration. The x- and y-components of velocity (at any time t) become
[[upsilon].sub.x] = [[upsilon].sub.0] cos [theta] and [[upsilon].sub.y] = [[upsilon].sub.0] sin [theta] - gt.
The expression for [[upsilon].sub.y] comes from replacing [[upsilon].sub.0] in Equation 1.1 with [[upsilon].sub.0] sin [theta]. Integrating these velocity components with respect to time, we can now determine the x- and y-components of the arrow's position at any time. These are given by
x = ([[upsilon].sub.0] cos [theta])t and y = ([[upsilon].sub.0] sin [theta])t -[gt.sup.2]/2.
We can now calculate the horizontal distance (the range) that the arrow will travel before striking the lion. Setting the y-component to zero (recall that the vertical height where the arrow strikes the lion is the same as the height of the arrow leaving the bow), we obtain
([[upsilon].sub.0] sin [theta])t -[gt.sup.2]/2 = 0.
So, solving for t, we find that either t = 0 or
t = (2[[upsilon].sub.0] sin [theta])/g. (1.2)
Substituting this expression for t into the x-component, we find that the distance the arrow travels is
[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII].
We can now solve for the speed at which the arrow leaves Hercules' bow, [[upsilon].sub.0]. Substituting in the launch angle ([theta] = 20?), range (200 meters), and gravitational constant (9.8 meters per second squared), we find that
[[upsilon].sup.2.sub.0] = 200 x 9.8/2 x sin 20? x cos 20?.
Evaluating and taking the square root of both sides,
[[upsilon].sub.0] [approximately equal to] 55.22 meters/second [approximately equal to] 198.79 kilometers/hour.
Therefore, Hercules must fire the arrow with an initial velocity of almost 200 kilometers per hour (125 miles per hour) from his mighty bow. This assumes that the speed of the arrow remains constant in flight (as mentioned above).
How long does it take the arrow to reach the lion after it leaves the bow? Substituting v0 55.22 meters per second into Equation 1.2, we find
t = 2[[upsilon].sub.0] sin [theta]/g = 2 x 55.22 x sin 20?/9.8 [approximately equal to] 3.85 seconds.
Unfortunately, Hercules discovers that "the beast [is] invulnerable," as Apollodorus writes. Hercules' arrow will not penetrate the lion's hide. To capture the mighty lion, Hercules moves to another task in this labor.
1.2.2. Hercules Closes the Cave Mouth
From Apollodorus:
And when the lion took refuge in a cave with two mouths, Hercules built up the one entrance and came in upon the beast through the other, and putting his arm round its neck held it tight till he had choked it; so laying it on his shoulders he carried it to Cleonae.
Task: To defeat the lion, Hercules must close up one cave entrance and attack the lion through the other. He finds several stacks of tiles nearby, each of which contains sets of regular polygons. There is one stack of equilateral triangles, one stack of squares, one stack of regular pentagons, one stack of regular hexagons, and one stack of regular octagons (see Figure 1.2). Which stack(s) of polygons will allow Hercules to construct an edge-to-edge tiling in order to close up the mouth of the cave with no two tiles overlapping?
Solution: Polygons are figures having many sides, usually four or more. A tiling is a covering of the entire plane with nonoverlapping figures. An edge-to-edge tiling is one in which the edge of a tile coincides completely with the edge of a bordering tile. We can assume that each entrance to the cave lies in a plane, so that the polygons can close it up by being stacked vertically edge upon edge (if possible). Hercules is not concerned with small gaps at the polygon/cave mouth interface.
Regular polygons were thought to have special meaning for the ancient Greeks, possibly beacuse of their simple yet high degree of symmetry. A regular polygon is a figure whose sides are equal and whose interior angles are also equal. Examples of regular polygons are equilateral triangles and squares. The ancient Greek philosopher Plato speculated that geometric solids formed from regular polygons (called polyhedra) were the shapes of the fundamental components of the physical universe. The word "polyhedra" also comes from the Greek and means "many faces." There are five basic Platonic solids: the tetrahedron, formed with 4 equilateral triangles; the cube, formed with 6 squares; the octahedron, formed with 8 equilateral triangles; the dodecahedron, formed with 12 pentagons; and the icosahedron, formed with 20 equilateral triangles. For the universe to be in harmony, there should be a one-to-one correspondence between the five solids and the primordial elements-earth, fire, water, and air. Therefore, Plato dedicated the dodecahedron (with its pentagonal faces) to the heavens and the rest to the planet Earth.
When Hercules takes a particular tile from one of the stacks, he measures the angles of the polygon. An interior angle is an angle formed between two adjacent sides of a polygon; an exterior angle is formed between one side and an extension of another side of a polygon. Figure 1.3 shows a few regular polygons with both interior and exterior angles depicted.
So, back to the task at hand, determining how many of each polygon can meet at a point. In order to have an edge-to-edge tiling, Hercules must fit the polygons together in such a way that their interior angles add up to 360? without overlap. Of the five regular polygons that are available to Hercules (triangle, square, pentagon, hexagon, and octagon), which may be used as an edge-to-edge tiling to block the mouth to the cave, thus trapping the Nemean lion inside? Each exterior angle in an n-sided polygon has 360/n degrees. As the number of sides of the polygon increases, the total of the interior angles also increases. In fact, the total of the interior angles is equal to (n - 2) x 180?. The table below lists the five regular polygons and their respective interior and exterior angles.
So, for any regular polygon having more than six sides, each interior angle must be greater than 120? and each exterior angle must be less than 60?. Notice that the octagon satisfies this requirement. Before we develop the solutions, photocopy Figure 1.2 and try to make a tiling with the regular polygons.
Let's start with the triangles. Six equilateral triangles come together at a single point. The sum of the interior angles is thus 6 x 60? = 360?. Hercules can use equilateral triangles to close the cave without overlap. Since the sum of the interior angles in a square is 4 x 90? = 360?, Hercules finds that squares will also suffice to close up the cave using an edge-to-edge tiling. What about the pentagon? If three pentagons come together, the sum of their interior angles will be 3 x 108? = 324?, so three pentagons would be too few. If four pentagons come together, the sum of their interior angles will be 4 x 108? = 432?, so four pentagons would be too many. Pentagons will not work.
(Continues...)
Excerpted from Mythematics by Michael Huber Copyright © 2009 by Princeton University Press. Excerpted by permission.
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Table of Contents
List of Figures xiiiforeword xv
Chapter 1: The First Labor: The Nemean Lion 1
1.1 The Tasks 2
1.1.1 Shooting an Arrow 2
1.1.2 Hercules Closes the Cave Mouth 2
1.1.3 Exercise: Zeus Makes a Deal 3
1.2 The Solutions 3
1.2.1 Shooting an Arrow 3
1.2.2 Hercules Closes the Cave Mouth 6
1.2.3 Exercise: Zeus Makes a Deal 10
Chapter 2: The Second Labor: The Lernean Hydra 13
2.1 The Tasks 13
2.1.1 One Head Replaced by Two 14
2.1.2 Cauterizing the Hydra 14
2.2 The Solutions 15
2.2.1 One Head Replaced by Two 15
2.2.2 Cauterizing the Hydra 17
Chapter 3: The Third Labor: The Hind of Ceryneia 20
3.1 The Tasks 20
3.1.1 Optimizing the Hind's Journey 21
3.1.2 Cerynitian Work 21
3.1.3 Exercise: Work with a Variable Force 21
3.2 The Solutions 22
3.2.1 Optimizing the Hind's Journey 22
3.2.2 Cerynitian Work 26
3.2.3 Exercise: Work with a Variable Force 27
Chapter 4: The Fourth Labor: The Erymanthian Boar 29
4.1 The Tasks 30
4.1.1 Exercise: The Centaurs' Wine 30
4.1.2 Chiron's Poison 30
4.1.3 The Capture of the Boar 31
4.2 The Solutions 31
4.2.1 Exercise: The Centaurs' Wine 32
4.2.2 Chiron's Poison 34
4.2.3 The Capture of the Boar 37
4.3 The Erymanthian Sudoku Puzzle 40
Chapter 5: The Fifth Labor: The Augean Stables 41
5.1 The Tasks 42
5.1.1 The Herds of Augeas 42
5.1.2 Exercise: Hydrostatic Pressure on the Stable Walls 43
5.1.3 Cleaning the Stables with Torricelli 43
5.2 The Solutions 43
5.2.1 The Herds of Augeas 43
5.2.2 Exercise: Hydrostatic Pressure on the Stable Walls 45
5.2.3 Cleaning the Stables with Torricelli 48
Chapter 6: The Sixth Labor: The Stymphalian Birds 53
6.1 The Tasks 53
6.1.1 The Spiral of Archimedes 54
6.1.2 Resonating Castanets 54
6.1.3 Exercise: Monte Carlo Shooting Scheme 55
6.2 The Solutions 55
6.2.1 The Spiral of Archimedes 55
6.2.2 Resonating Castanets 59
6.2.3 Exercise: A Monte Carlo Shooting Scheme 64
Chapter 7: The Seventh Labor: The Cretan Bull 69
7.1 The Tasks 69
7.1.1 Exercise: Riding the Bull 70
7.1.2 The Marathon Attacks 70
7.2 The Solutions 70
7.2.1 Exercise: Riding the Bull 70
7.2.2 The Marathon Attacks 73
Chapter 8: The Eighth Labor: The Horses of Diomedes 76
8.1 The Tasks 76
8.1.1 Driving the Mares to the Sea 77
8.1.2 Hercules' Slingshot 77
8.1.3 Exercise: The City of Abdera 78
8.2 The Solutions 78
8.2.1 Driving the Mares to the Sea 78
8.2.2 Hercules' Slingshot 81
8.2.3 Exercise: The City of Abdera 83
8.3 The Diomedes Sudoku Puzzle 87
Chapter 9: The Ninth Labor: The Belt of Hippolyte 89
9.1 The Tasks 90
9.1.1 The Sons of Minos versus Hercules 91
9.1.2 The Amazons and the Spread of a Rumor 91
9.1.3 Exercise: Hercules and the Kraken 92
9.2 The Solutions 92
9.2.1 The Sons of Minos versus Hercules 92
9.2.2 The Amazons and the Spread of a Rumor 98
9.2.3 Exercise: Hercules and the Kraken 101
Chapter 10: The Tenth Labor: Geryon's Cattle 104
10.1 The Tasks 105
10.1.1 The Pillars of Hercules 106
10.1.2 The Golden Goblet 106
10.1.3 Hera Sends the Gadflies 106
10.1.4 Blocking the River Strymon 107
10.2 The Solutions 107
10.2.1 The Pillars of Hercules 107
10.2.2 The Golden Goblet 110
10.2.3 Hera Sends the Gadflies 112
10.2.4 Blocking the River Strymon 114
Chapter 11: The Eleventh Labor: The Apples of the Hesperides 118
11.1 The Tasks 120
11.1.1 Exercise: The Riddles of Nereus 120
11.1.2 Wrestling Antaeus 121
11.1.3 Exercise: Hercules Has the Whole World in His Hands 121
11.2 The Solutions 122
11.2.1 Exercise: The Riddles of Nereus 122
11.2.2 Wrestling Antaeus 125
11.2.3 Exercise: Hercules Has the Whole World in His Hands 131
Chapter 12: The Twelfth Labor: Cerberus 134
12.1 The Tasks 135
12.1.1 The Descent into the Underworld 135
12.1.2 The Fight with Cerberus 135
12.2 The Solutions 136
12.2.1 The Descent into the Underworld 136
12.2.2 The Fight with Cerberus 139
12.3 The Cerberus Sudoku Puzzle 143
Appendix A: The Labors and Subject Areas of Mathematics 147
A.1 Subject Areas by Labors and Tasks 147
A.2 Tasks by Subject Area 149
Appendix B: Hercules before the Labors 151
B.1 Hercules' Background 151
Appendix C: The Authors of the Hercules Myth 154
C.1 The Authors 154
C.2 The Lay of the Labours of Hercules 156
Appendix D:The Laplace Transform 161
D.1 Initial Value Problems and the Laplace Transform 161
D.1.1 Theory 161
D.1.2 An Example 163
Appendix E: Solution to the Sudoku Puzzles 164
Bibliography 167
Index 171
What People are Saying About This
Michael Huber ingeniously introduces many elementary mathematical and physical problems in this fascinating book. Who knew Greek mythology could be so mathematical!
— John Adam, coauthor of "Guesstimation"
This book does an excellent job of blending math with a very different field—classics. As I read the book I thought, 'Had one of the gods offered Hercules a premonition of this book's contents, he would have quickly trained to have strength in mathematical insights to rival his physical prowess.' The book repeatedly underscores the importance of careful mathematical modeling.
— Tim Chartier, Davidson College
In this one-of-a-kind book, Michael Huber converts the Twelve Labors of Hercules into a series of math problems, thereby demonstrating the chops of an applied mathematician and the sensibility of a classicist. We can only hope that, for a sequel, Huber takes on A Thousand and One Nights.
— William Dunham, author of "The Calculus Gallery"
I like the concepts underlying the problems in this book. It will be a valuable resource for classroom teachers at all levels and a fun read for students.
— John Quintanilla, University of North Texas
Huber has come up with a clever means to present some pretty mathematics and math modeling. Covering an eclectic set of topics, this book will teach readers a golden goblet's worth of mathematics.
— Colin Adams, coauthor of "How to Ace Calculus"
"In this one-of-a-kind book, Michael Huber converts the Twelve Labors of Hercules into a series of math problems, thereby demonstrating the chops of an applied mathematician and the sensibility of a classicist. We can only hope that, for a sequel, Huber takes on A Thousand and One Nights."—William Dunham, author of The Calculus Gallery"Huber has come up with a clever means to present some pretty mathematics and math modeling. Covering an eclectic set of topics, this book will teach readers a golden goblet's worth of mathematics."—Colin Adams, coauthor of How to Ace Calculus"Michael Huber ingeniously introduces many elementary mathematical and physical problems in this fascinating book. Who knew Greek mythology could be so mathematical!"—John Adam, coauthor of Guesstimation"This book does an excellent job of blending math with a very different field—classics. As I read the book I thought, 'Had one of the gods offered Hercules a premonition of this book's contents, he would have quickly trained to have strength in mathematical insights to rival his physical prowess.' The book repeatedly underscores the importance of careful mathematical modeling."—Tim Chartier, Davidson College"I like the concepts underlying the problems in this book. It will be a valuable resource for classroom teachers at all levels and a fun read for students."—John Quintanilla, University of North Texas