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Website last updated 03 August, 2010

ST Scale

A decimal trig scale with angles for sines or tangents 0.6º-6º running in one direction, and angles for cosines or cotangents 89.4º - 84º running the other way, with all values a little bit off.

Precision Warning

As you can see in the diagram, ST, S2, and T2 are all essentially the same scale, the only differences are when zoomed. This is because in those degree ranges, sin and tan are close enough to use one scale on a normal slide rule.

However, sin and tan values are not close enough when large zooms are used, and so we provide two nonstandard scales as well: S2, which is calculated strictly from the sine function, and T2, which is pure tangent function. ST is included for those who wish to reproduce the scales of an existing slide rule and don't use zoom or lots of decimal places. ST's values are calculated as an average of the sin and tan functions so they will always be slightly wrong, just like on the real thing. The inaccuracies become more pronounced towards the right end of the scale.

Read tutorial on Trigonometry.

S2_D, ST_D, and T2_D are the DMS equivalent scales, and the above discussion applies to them as well.