HEMMI SLIDE RULE CO. LTD., Tokyo / Japan                      (1971)
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S C A L E S   of the Bamboo-Based   HEMMI / ODELCO   Model  » 255D «
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Front Side               [ inverse / RED ]                 Back Side
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L          lgX                        Sh1     SinH(0.1X)
K          X3                         Sh2     SinH(X)
                                      Th      TanH(X)
DF         πX                         A       X2
--------------------------------------------------------------------
CF         πX                         B       X2
[CIF]      [1/πX]                     TI2     [tan(X)]; tan(0.1X)
                                      TI1     [tan(0.1X)]; tan(X)
[CI]       [1/X]                      SI      [sin(0.1X)]; cos(0.1X)
C          X                          C       X
--------------------------------------------------------------------
D          X                          D       X
LL3        exp(X)                     [DI]    [1/X]
LL2        exp(0.1X)                  Χ       (=Chi) Radians
LL1        exp(0.01X)                 Θ       (=Theta) Degrees

R E M A R K S :
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The reciprocal SI, TI1 or TI2 refer to the reciprocal CI(DI) scales:

Black Numbers on TI1/2-Scale  refer to    RED Results on CI/DI-Scale
  RED Numbers on TI1/2-Scale  refer to  BLACK Results on C/D-Scale
Black Numbers on    SI-Scale  refer to    RED Results on CI/DI-Scale
  RED Numbers on    SI-Scale  refer to    RED Results on CI/DI-Scale

Example:  12 * sin(34°)  =  6.71
--------
Set sin(34°) opposit to 12 on D scale (="division" operation) and
read the result on D scale under the right "1" of the slider.
 
The DEFINITIVE FORMS for the HYPERBOLIC FUNCTIONS are:
------------------------------------------------------
CosH(X) = ( exp(+X) + exp(-X) ) / 2   <==  this is the "Chain Line"
SinH(X) = ( exp(+X) - exp(-X) ) / 2       ( eg. suspension bridge )
TanH(X) =  SinH(X)  / CosH(X)
 exp(X) =  SinH(X)  + CosH(X)
      1 =  CosH2(X) - SinH2(X)

CosH(X) = sqrt( 1 + SinH2(X) )  =  SinH(X) / TanH(X)

Using the Hyperbolic Functions:
Start with value on the Sh scales ==>> reading SinH on D scale,
  start with value on the D scale ==>> reading ArcSinH on Sh.
Start with value on the Th scale  ==>> reading TanH on D scale,
  start with value on the D scale ==>> reading ArcTanH on Th.

Example:  CosH(0.345)  =  SinH(_) / TanH(_)  =  1.060
--------
Set the left "1" of the slider under TanH(0.345). Move the hairline
to SinH(0.345) and read the result on C (!) scale. YES! It's clever: 
This C scale is the "difference"  SinH(_) - TanH(_) and - because of
log. scales - represents the quotient of its values.


This famous slide rule came in a brown leather case together with an
instruction booklet. The ODELCO logo (only on the slide rule's front,
right on top) refer to the distributor of HEMMI in the Philippines.

HEMMI introduced a year code, starts with  1950 = "A" ...   and the
month code starts with  January = "A" ...
This slide rule has the code "YI", means it is made in Sept. 1974.

                      Historical Remarks ...
impressum:
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© C.HAMANN       http://public.BHT-Berlin.de/hamann         12/25/06