 # about slide So let us launch

## Found at: sdf.org:70/users/melton/phlog/slide-rule-revisited

```The Slide Rule and the neighborhood
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```about slide rules.  So let us launch into another problem involving
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```than punching the numbers in on the calculator.
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```Our man is standing atop a 300 ft. ocean front cliff and observes a
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```We'll refer back to our handy table for solutions to right
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```triangles.  There are a couple of approaches we can take, but in
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```this case since we are given the angle of depression, we'll subtract
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```that from 90° to give us our remaining angle which is 78°.
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```To determine the distance from the base of the cliff to the boat
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```(we'll call it 'a'), we multiply 300 * (TAN 78°) = a.  So first
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```let us find the tangent of 78° on the slide rule.  Hmm...the
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```tangent scale only goes from 5.7° to 45°.  Let us see what
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```one of my slide rules (Sterling Acumath 400) provides a solution:
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```So if we follow this path then 90°-78°=12°.  Back to
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```Now we need the reciprocal of .212.  Here we go to the 'CI' and 'D'
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```To determine the decimal point when finding reciprocals one of the
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```To find y = 1/x:
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```- Convert x to scientific notation and read it's coefficient c and
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`t's exponent, p`
```- if the coefficient is 1 or -1 exactly, y exponent is -p
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```- otherwise y's exponent is -p-1
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```To get our decimal in the correct place, we convert .212 to
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```Acumath slide rule the 'CI' scale is on the slide.  We place the
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```cursor over 2.12 on the CI scale (remembering the 'CI' scale
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`ncreases from right to left) and read down to the 'D' scale which`
```neither 1 or -1, the exponent of our answer is -(-1)-1 = 0 so our
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`t out.  Now we multiply the height of the cliff (300 or 3E2) times`
```the tangent of 78° which we just figured out is 4.71E0.  On the
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```the 'D' scale:
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```Then we move the cursor over to 4.71E0 on the 'C' scale and read our
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```answer directly below on the 'D' scale, in this case, 1.42.
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```Now we add the exponents 0 + 2 = 2, but since we have to adjust for
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```the change of magnitude (3 * 4.71 > 10), We add one to the exponent
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```(0 + 2 + 1 = 3).  Our answer is 1.42E3 or 1420.  What does the
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```calculator tell us?
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```and calibration.  The additional factor is the user's ability to set
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`t and read the values.  For most applications, three significant`
```figures is good enough.
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```Now that we have gone through this seemingly tedious exercise, I am
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```the mathematical equivalent to stopping and smelling the roses.  In
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```our rush for an instant answer or instant gratification, we miss out
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```on the intimate details of the journey.  In a similar way, it is
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```like the difference between hopping in our car and driving to the
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```local market for our groceries, or slowing down and taking the
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```bicycle or even walking and have more intimate contact with the
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```neighborhood and surroundings.  As I have mentioned in a previous
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```a simple tool like the scythe allows one not only to mow grass and
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`ntimate with the subtleties of the land (and wildlife) that would`
```otherwise be lost when sitting in a tractor noisily masticating the
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```on a journey to an answer and on the trip, we become more familiar
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```the Luddites only destroyed machines that did not support or foster
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```the "commonality."  Sometimes I find myself pausing and reflecting
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`f a particular technology I am using meets that standard, or have I`
```become a slave to that particular device and all of its ancillary
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