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# Cómo construir una regla de cálculo

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### Cómo construir una regla de cálculo

1. 1. n. “ ¡un iWii‘. ' I? En v ¡‘Z Ji", ‘¡unía Stopping Birth of Future B. . n Irs" uÍ-Xn’- ti. l ¡. . i 1 . y s 4 , . _ . .__ . - , ._. . "' " . . ‘ e u _. n , - y. v‘ ‘d, .'. °_*. . '- -‘ --. : ‘_l _ . - s ' _ g: i. "4 * _. «-' , _ . -_. r : . _ . N ' . _ , .. _. i. - . . ü.o n" ‘- _ . .-' J - . -, . _'. r , i. i. ‘ _ , 2'! ‘ x ' l a» x. °. ,_J . ‘Z i .1 . r/ A . ,__ -34 Bringing DNA Computers to Life MAY 2008 WWWSCIAMIÏOM - ‘n u . ._ I _, .. . r A ‘ ‘ z "j . _ ‘u, o n‘ nt ' 1 A 4 J _. ¡.“ a 4 v . ,. I . v A’. _i ', g‘ , . . - ' -_ I - . 1a‘ n ‘ '- -. , . « . , , l . — . i 1V vt i‘ _ _ . ' Q N I‘ _ i _. ¡. . I» ' I i v . . , . -_ -2 ' . - . . y , ’ _. ".
2. 2. Before electronic calculators, the mechanical slide rule dominated scientific and engineering computation Wíﬂwo generations ago a standard uníform identiﬁed engi- neers: white shirt, narrow tie, pocket protector and slide l‘ rule. The shirt and tie evolved into a T-shirt Sporting some software advertisement. The pocket protector has been re- placed by a cell phone holster. And the slide rule has become an electronic Calculator. Take another look at that slide rule. Pull it out of the drawer you stashcd it in 30 years ago or make one of your own [see box on next page]. You’ll see why it was once so valuable. Before the 1970s the slide rule, or slipstick, was as common as the typewriter or the mimeograph machine. A few seconds of ﬁddling let scientists and engíneers multiply, divide and ﬁnd square and cube roots. With a bit more effort, techies could also computo ratios, ínverses, sínes, cosines and tangents. Q Inscribed with a dozen or more function scales, the slide rule symbolizcd the mystcríes of arcane science. Truth is, though, two scales did most of the‘ work, as many technical jobs boilcd down to multíplícation and division. A pianíst might play most of the ívories on the keyboard, but rarely did any engineer use all the scales on his (almost never her) slide rule. Some engíneers, perhaps bucking for promotion, wielded slide rules made of exotíc mahogany and boxwood; others sported rules fashioned from ivory, aluminum or ﬁberglass. Cheapskatcswincludíng this author-carried plastic ones. From the ﬁncst to, the humblest, howevcr, all slide rules were based on logarithms [see box on page 85]. Birth ofthe Slide Rule JOH N N A m ER, a Scottish mathemarícian, physicist and as- tronomer, invented logarithms in 1614. His Canon of Loga- rithms begins: “Seeíng there is nothing that is so troublesome to mathematical practice, nor doth more molest and hínder cal- culators, than the multiplications, dívisions, square and cubical SClENTlFlC AMERlCAN HRAD DECECEO
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4. 4. fhljirí ¡rm L You can build a working slide rule from paper and cellophane tape. Photocopging these plans onto thicker paper gields a reasonablg robust calculating instrument. These construction plans are also available at wwwsciamcom/ ontheweb a Cut here —[ c Cut here ASSEMBLY INSTRUCTIONS X lgx sin COS l 1 1 x [In- Right-hand index h Cut out the entirewhite n”: panel [a]. Cut alongline between parts Aand B [b], then remove excess [c]. 1 1.0 l 60 1o 90 30 20 O CHRIS HAMANN AND NANCY SHAW b Cut here ° i lunluuluu llllllll Fold partA along the 9- dotted lines. 50 40 l| llll| llll| llll| llll| lllI 1.5 a Slip part B intothe folded i} partA. TH L To make the cursor [the " ‘rfslidingwindowthatis inscribed with a hairline], use the guides to the left to measure two pieces of transparent tape. Make one section thelength ofthe black line and the otherthe length ofthe red line. Place the adhesive sides together. l| I|I| I|I| I|I| l|I| l|l| lIlI| Il 7 1 2 quuuur l| l|l| l|lllll| l|l| l|llll| llll| llll| llll| lll n 2 IIIlIIIIII llilililllll Illlllllllll i? 5 ¿- Drawa line with aline J markerin the middle. n ¡nuuuu 5 2 Illlllllllll 311’ ll| llll| llll| llll| l 6 Í‘ Wrap the folded tape ‘ around the slide rule forsizing. Usethe adhesive end to complete the cursor. Slide cursorontothe rule. l| IIII| ||lI| |_IIl| l 2 1.5 III A— 84.5 5.5 e Inululil ¡mu l| ||l| ||I| ||l| I 9 1 -]| l|I| lIll| IlII| Il| l|lIl [Slider] Completed cursor B C Left-hand index 3’ 3 e o - u u . v u . n b u n n . n n n n n n n b n n . n n l . b n e a n n n e . 4 u n . u u n . n n u . - A . - b a a - n n u e 82 SClENTIFIC AMERICAN MAY 2005