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Accuracy

Most users have their "standard" ways of checking the accuracy of a rule. For some scales this is easy; for example 3 x 3 equals 9 and sin 30 equals 0.5. For other scales, tan and CF (p shifted) this is not as easy as there are no simple comparisons. The following table gives details of marks which will line up for the other scales and the precision of the alignment. As can be seen, in all cases the precision is much better than 1 : 27 000.

It should be noted that the alignments for log-log scales do not work for all rules as the figures assume that the rule are based on natural (Naperian) logarithms.

Scale Description Value C/D scale Precision
Sin Sine 30 0.5 Exact
Tan1 Tangent < 45 19.90 0.362 1 : 71 000
Tan2 45 < tangent < 85 82.20 7.30 1 : 42 000
Logs log base 10 3.02 .48 1 : 77 000
CF p shifted 7.10 2.26 Almost exact
W 10 shifted 7.40 2.34

1 : 27 000

P Pythagorean  (1- x2) 0.6 0.8 Exact
LL3 log-log, 2.7 to 5 x 105 (log base e) 8.50 2.14 1 : 32 000
LL2 log-log, 1.1 to 2.7 (log base e) 1.60 0.470 1 : 125 000
LL1 log-log, 1.01 to 1.1 (log base e) 1.0142 0.0141 1 : 110 000