3.7) <strong>The</strong> Five Pillars of TrigonometryLanguage is an innate human activity, andmathematics can be defined as the language ofmeasurement! This definition makes perfect sense, forhumans have been both measuring and speaking/writingfor a very long time. Truly, the need to measure is in our‘blood’ just as much as the need to communicate.Trigonometry initially can be thought of as the mathematicsof ‘how far’, or ‘how wide’, or ‘how deep’. All of the precedingquestions concern measurement, in particular, themeasurement of distance. Hence, trigonometry, as originallyconceived by the ancients, is primarily the mathematicalscience of measuring distance. In modern times,trigonometry has been found to be useful in scores of otherapplications such as the mathematical modeling andsubsequent analysis of any reoccurring or cyclic pattern.Geometry, particularly right-triangle or <strong>Pythagorean</strong>geometry, was the forerunner to modern trigonometry.Again, the ancients noticed that certain proportionsamongst the three sides of two similar triangles (triangleshaving equal interior angles) were preserved—no matter thesize difference between the two triangles. <strong>The</strong>se proportionswere tabulated for various angles. <strong>The</strong>y were then used tofigure out the dimensions of a large triangle using thedimensions of a smaller, similar triangle. This onetechnique alone allowed many powerful things to be donebefore the Common Era: e.g. construction of the GreatPyramid, measurement of the earth’s circumference (25,000miles in today’s terms), estimation of the distance from theearth to the moon, and the precise engineering of roadways,tunnels, and aqueducts. ‘Nascent trigonometry’, in the formof right-triangle geometry, was one of the backbones ofancient culture.In modern times trigonometry has grown far beyondits right triangle origins. It can now be additionallydescribed as the mathematics describing periodic or cyclicprocesses.116
One example of a periodic process is the time/distancebehavior of a piston in a gasoline engine as it repeats thesame motion pattern some 120,000 to 200,000 times in anormal hour of operation. Our human heart also exhibitsrepetitive, steady, and cyclic behavior when in good health.Thus, the heart and its beating motion can be analyzedand/or described using ideas from modern trigonometry ascan any electromagnetic wave form.Note: On a recent trip to Lincoln, Nebraska, I calculated that thewheel on our Toyota would revolve approximately 1,000,000 timesin a twelve-hour journey—very definitely a cyclic, repetitive process.Returning to measurement of distance, look up tothe night sky and think ‘how far to the stars’—much likeour technical ancestors did in ancient Greece, Rome,Babylon, etc. Trigonometry has answered that question inmodern times using the powerful parallax technique. <strong>The</strong>parallax technique is a marriage of modern and old: careful,precise measurement of known distances/anglesextrapolated across vast regions of space to calculate thedistance to the stars. <strong>The</strong> Greeks, Romans, andBabylonians would have marveled! Now look down at yourGPS hand-held system. Turn it on, and, within a fewseconds, you will know your precise location on planetearth. This fabulous improvement on the compass operatesusing satellites, electronics, and basic trigonometry asdeveloped from right triangles and the associated<strong>Pythagorean</strong> <strong>The</strong>orem. And if you do not have a GPS device,you surely have a cell phone. Every fascinating snippet ofcellular technology will have a mathematical foundation intrigonometry and the <strong>Pythagorean</strong> <strong>The</strong>orem.Trigonometry rests on five pillars that areconstructed using direct <strong>Pythagorean</strong> principles or derivatesthereof. <strong>The</strong>se five pillars serve as the foundation for thewhole study of trigonometry, and, from these pillars, onecan develop the subject in its entirety.Note: In 1970, while I was in graduate school, a mathematicsprofessor stated that he could teach everything that there is to knowabout trigonometry in two hours. I have long since realized that heis right. <strong>The</strong> five <strong>Pythagorean</strong> pillars make this statement so.117
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The PythagoreanTheoremCrown Jewel o
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The Pythagorean TheoremCrown Jewel
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Table of ContentsList of Tables and
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List of Tables and FiguresTablesNum
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Figures…continuedNumber and Title
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List of Proofs and DevelopmentsSect
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PrefaceThe Pythagorean Theorem has
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1 : 2x2x2****22 13x 7 13x 7 0 : a
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1) Consider the Squares“If it was
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s090045 0ss45450450090Figure 1.3: O
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Notice that the right-triangle prop
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The middle square (minus the donut
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Our proof in Chapter 1 has been by
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2) Four Thousand Years of Discovery
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The proof Pythagoras is thought to
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cabcFigure 2.4: Annotated Square wi
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Figure 2.6 is the diagram for a sec
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1x:b2:Area(CBA)3:Area( ABC)Area(ABC
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Euclid’s proof of the Pythagorean
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First we establish that the two tri
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1 2y b b: y b c c2:A3:A4:Aunshaded
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XB'A090 CBFigure 2.12: Euclid’s C
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2.3) Liu Hui Packs the SquaresLiu H
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One of my favorites was Boxel, a ga
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2.4) Kurrah Transforms the Bride’
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Note: as is the occasional custom i
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2.5) Bhaskara Unleashes the Power o
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2.6) Leonardo da Vinci’s Magnific
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In Figure 2.24, we enlarge Step 5 a
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But, this is precisely the nature o
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2.8) Henry Perigal’s TombstoneHen
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In the century following Perigal, b
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- Page 73 and 74: B 2← γ →α y βx C-xC 2Figure
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- Page 79 and 80: Sincexcpwas chosen on an arbitrary
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- Page 85 and 86: 2.11) Shear, Shape, and AreaOur las
- Page 87 and 88: Step 1: Cut the big square into two
- Page 89 and 90: In Table 2.3, we briefly summarize
- Page 91 and 92: We can formally state this similari
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- Page 95 and 96: There are three Pythagorean-triple
- Page 97 and 98: Thus, if we multiply any given prim
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- Page 103 and 104: 3.5) Pythagoras and the Three Means
- Page 105 and 106: yxy MHxab2ab2 y x FC y ab2ab 2ab y
- Page 107 and 108: Hero was the founder of the Higher
- Page 109 and 110: 5 : Solve for area using the formul
- Page 111 and 112: 4 : Construct the parallelogram wit
- Page 113 and 114: We already have introduced Thabit i
- Page 115 and 116: Some historians believe Stewart’s
- Page 117: In pre-computer days, both all four
- Page 121 and 122: The six trigonometric functions are
- Page 123 and 124: The following four relationships ar
- Page 125 and 126: As with any set of identities, the
- Page 127 and 128: Figure 3.17 can be used as a jumpin
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- Page 131 and 132: a2Law of Cosines c2 b2 2bccos()The
- Page 133 and 134: An example of a Diophantine equatio
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- Page 138 and 139: 4) Pearls of Fun and WonderPearls o
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- Page 148 and 149: The four-step solution follows. All
- Page 150 and 151: Figure 4.9 depicts Eratosthenes’
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- Page 158 and 159: BD ACtan( 21 )Even for the closest
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- Page 162 and 163: Figure 4.16: Triangular Phi---The h
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Epilogue: The Crown and the Jewels
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Not only has it endured, but the Py
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A] Greek AlphabetGREEK LETTERUpper
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C] Geometric FoundationsThe Paralle
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8. Congruent Triangles: Two triangl
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3. Rectangle: A bh : P 2b 2h, b &
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Recreational Mathematics11. Pickove
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GGolden RatioDefined and algebraica
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Puzzles (cont)Pythagorean Magic Squ
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Pythagorean Theorem ProofsAlgebraic
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Trigonometry (cont)Eratosthenes mea