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Facsimile / facsimile

Facsimile Simulation Library
http://facsim.org/
GNU Lesser General Public License v3.0
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Angle measurements should be unitless #26

Closed Facsimiler closed 5 years ago

Facsimiler commented 8 years ago

Currently, Facsimile has a measurement family for angles, as that seemed to be the most straightforward means of implementing support for this measurement type. However, angles are really unitless.

This seems counter-intuitive, since angles can be measured in radians, degrees, etc. However, consider the definition of radian meansure: arc length / radius. Both of these terms are measured as lengths, so dividing a length by a length results in a unitless result.

For example, say we have an arc length of τ/4 meters, and a radius of 1 meter. This would subtend an angle of (τ/4 m)/(1 m), resulting in an angle of τ/4 radians (but, which is unitless, in the sense that it's not expressed in terms of primary SI units). As you might expect, angles are not a primary SI unit.

That said, we can express the scale of an angle in different measurement units, as radians, degrees, revolutions, etc. But angles, as a family, are unitless.

Facsimiler commented 5 years ago

Closing, as no longer relevant.