The Pythagorean Theorem - Educational Outreach

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As the reader can immediately discern, this proof, aDRIII, is not visually apparent. Algebra must be used alongwith the diagram in order to quantify the neededrelationships and carry the proof to completion.Note: This is not a good proof for beginning students—say youraverage eighth or ninth grader—for two reasons. One, the algebra issomewhat extensive. Two, derived and not intuitively obviousquantities representing various lengths are utilized to formulate thevarious areas. Thus, the original Pythagorean proof remainssuperior for introductory purposes.Our last proof in this section is a four-step DRVdeveloped by a college student, Michelle Watkins (1997),which also requires similarity principles to carry the proofto completion. Figure 2.7 shows our two fundamental,congruent right triangles where a heavy dashed lineoutlines the second triangle. The lighter dashed linecompletes a master triangle ABC for which we willcompute the area two using different methods. The reader isto verify that each right triangle created by the merger of thecongruent right triangles is similar to the original righttriangle.Step 1 is to compute the length of line segment xusing similarity principles. The two distinct areacalculations in Steps 2 and 3 result from viewing the mastertriangle as either ABC or CBA . Step 4 sets the equalityand completes the proof.CAcabxBFigure 2.7: Twin Triangle Proof34
1x:b2:Area(CBA)3:Area( ABC)Area(ABC)4:c212c aset2 122ba2b x a b{ a2212 b a( c)(c)2 b( a)a aa( a)221212} b22 ba c2122 c2 12{ a22 b }One of the interesting features of this proof is thateven though it is a DRV, the five individual areas were notall needed in order to compute the area associated withtriangle ABC in two different ways. However, some areaswere critical in a construction sense in that they allowed forthe determination of the critical parameter x. Other areastraveled along as excess baggage so to speak. Hence, wecould characterize this proof as elegant but a tad inefficient.However, our Twin Triangle Proof did allow for theintroduction of the construction principle, a principle thatEuclid exploited fully in his great Windmill Proof, thesubject of our next section.35
Page 1: The PythagoreanTheoremCrown Jewel o
Page 4: The Pythagorean TheoremCrown Jewel
Page 7 and 8: Table of ContentsList of Tables and
Page 9 and 10: List of Tables and FiguresTablesNum
Page 11 and 12: Figures…continuedNumber and Title
Page 13 and 14: List of Proofs and DevelopmentsSect
Page 15 and 16: PrefaceThe Pythagorean Theorem has
Page 17 and 18: 1 : 2x2x2****22 13x 7 13x 7 0 : a
Page 19 and 20: 1) Consider the Squares“If it was
Page 21 and 22: s090045 0ss45450450090Figure 1.3: O
Page 23 and 24: Notice that the right-triangle prop
Page 25 and 26: The middle square (minus the donut
Page 27 and 28: Our proof in Chapter 1 has been by
Page 29 and 30: 2) Four Thousand Years of Discovery
Page 31 and 32: The proof Pythagoras is thought to
Page 33 and 34: cabcFigure 2.4: Annotated Square wi
Page 35: Figure 2.6 is the diagram for a sec
Page 39 and 40: Euclid’s proof of the Pythagorean
Page 41 and 42: First we establish that the two tri
Page 43 and 44: 1 2y b b: y b c c2:A3:A4:Aunshaded
Page 45 and 46: XB'A090 CBFigure 2.12: Euclid’s C
Page 47 and 48: 2.3) Liu Hui Packs the SquaresLiu H
Page 49 and 50: One of my favorites was Boxel, a ga
Page 51 and 52: 2.4) Kurrah Transforms the Bride’
Page 53 and 54: Note: as is the occasional custom i
Page 55 and 56: 2.5) Bhaskara Unleashes the Power o
Page 57 and 58: 2.6) Leonardo da Vinci’s Magnific
Page 59 and 60: In Figure 2.24, we enlarge Step 5 a
Page 61 and 62: But, this is precisely the nature o
Page 63 and 64: 2.8) Henry Perigal’s TombstoneHen
Page 65 and 66: In the century following Perigal, b
Page 67 and 68: Returning to Henry Perigal, Figure
Page 69 and 70: Figure 2.32 is President Garfield
Page 71 and 72: Even though the Cartesian coordinat
Page 73 and 74: B 2← γ →α y βx C-xC 2Figure
Page 75 and 76: Being polynomial in form, the funct
Page 77 and 78: Thus, the critical point ( C 2 ,0)i
Page 79 and 80: Sincexcpwas chosen on an arbitrary
Page 81 and 82: ∂F/∂x = ∂F/∂y = 0x(C - x) 2
Page 83 and 84: Define a new function21 A2 A3 2xcp
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
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We can formally state this similari
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What we will do in Section 3.2 is p
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There are three Pythagorean-triple
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Thus, if we multiply any given prim
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The last equality shows that the in
Page 101 and 102:
A Pythagorean Quartet is a set of f
Page 103 and 104:
3.5) Pythagoras and the Three Means
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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
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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 and 118:
In pre-computer days, both all four
Page 119 and 120:
One example of a periodic process i
Page 121 and 122:
The six trigonometric functions are
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The following four relationships ar
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As with any set of identities, the
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Figure 3.17 can be used as a jumpin
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The remaining two pillars are the L
Page 131 and 132:
a2Law of Cosines c2 b2 2bccos()The
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An example of a Diophantine equatio
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However, Euler’s Conjecture did n
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4) Pearls of Fun and WonderPearls o
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We have achieved five-digit accurac
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140212213116)74370116)(74370(370)74
Page 144 and 145:
X X X X O X X O X XO X X O O OO X O
Page 146 and 147:
4.3) Earth, Moon, Sun, and StarsIn
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The four-step solution follows. All
Page 150 and 151:
Figure 4.9 depicts Eratosthenes’
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---High above the earth, we see the
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The commonly accepted value is abou
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1BC : tan( BAC)BABC BAtan(BAC)0BC
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BD ACtan( 21 )Even for the closest
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3w 2h s w 5 s w 0.38196s&5 1s
Page 162 and 163:
Figure 4.16: Triangular Phi---The h
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What remains to be done is to devel
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3 : h32 4 h222 2 24C 2 h33162 2 2
Page 168 and 169:
Epilogue: The Crown and the Jewels
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Not only has it endured, but the Py
Page 172 and 173:
A] Greek AlphabetGREEK LETTERUpper
Page 174 and 175:
C] Geometric FoundationsThe Paralle
Page 176 and 177:
8. Congruent Triangles: Two triangl
Page 178 and 179:
3. Rectangle: A bh : P 2b 2h, b &
Page 180 and 181:
Recreational Mathematics11. Pickove
Page 182 and 183:
GGolden RatioDefined and algebraica
Page 184 and 185:
Puzzles (cont)Pythagorean Magic Squ
Page 186 and 187:
Pythagorean Theorem ProofsAlgebraic
Page 188:
Trigonometry (cont)Eratosthenes mea
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The Pythagorean Theorem - Educational Outreach

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