Using a Slide Rule
Everybody chill the %&*$& out I got it!
8 + 6 = 14
Can do addition!
And subtraction!
But what about
Multiplication?
Division?
Square roots?
Exponents?
Sine/cosine?
Etc?
Log scale: “addition” → multiplication
“subtraction” → division
2
x 3
=6
Stock
• Pickett Microline 160-ES
• Very basic rule
– Multiplication, Divison
– Square, square root
– Cube, cube root
– Common logs (base-10)
Slider
Cursor
More sophisticated rules have
more scales!
Duplex rule: printed on both sides
• Only calculates mantissa, not exponent
X
– Mentally find order of magnitude
2.437 x 1023
– Get a “feel” for the sizes of things!
• 2-3 sig figs
– Use interpolation
3.141592653589793
vs.
– Each digit is harder to get than the last!
3.1415926535897932
– Get a “feel” for what accuracy means!
Factor of 10!
• Multiple operations in one “step”
Not just “one
extra digit”
– 2/ , 1/sin(xy) , (ab)3
– 2.134 x 3.57, 2.134 x 4.37, 21.34 x 437
• Need to be aware of properties of trig functions, logs, exps
– Must apply identities, etc.
• No addition or subtraction
– Do that by hand!
• Longer learning curve
– You get better with practice!
• Commonly used scales:
Reads
from right
to left!
–
–
–
–
Most important scales!
C,D: base scales: Multiplication, division
CF, DF: scales folded at : Operations involving  in one step!
CI, DI: inverted scales: Reciprocals in one step!
Trig:
Problem: trig functions cover >1 order of magnitude
Also CIF, DIF
sometimes
• S: sine 5.7 <  < 90
0.1 < sin,cos() < 1
cos 0 <  < 84.3 red scale on S
C: 0.1 < tan,cot() < 1
uses
• T: tan 5.7 <  < 45 (use CI for 45< <84.3)
CI: 10 > tan,cot() > 1
sin()  tan()
cotan: reverse use of C, CI from tan
• ST: sin,tan for  < 5.7 (cos/cot for large )
– Alternate: use sin,tan()   (with R marker) for smaller angles
–
–
–
–
A,B: doubled scales: squares, square roots
K: tripled scale: cubes, cube roots
L: log scale: 10x or log10(x) (Ln: natural logs)
LLn, LL0n (or –LLn): log-log scale LL0: e0.001x
• Natural logs / exponents
• Arbitrary exponents: yx
• Sometimes seen as ZZn, ZZ0n…
LL1: e0.01x
LL2: e0.1x
LL3: ex
LL0n: e-…x (i.e. 1/LLn)
Slide rule simulator!
• http://www.antiquark.com/sliderule/sim/