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>> The writer don’t seem to realise that radian is not an arbitrary unit but a dimensionless one which is defined so that 1rad is actually just 1.

It's been a while, but I used to have an argument that rad should be a unit. This even plays well in physics where it allows torque to not have the same units as a joule.

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I don't see how radians come into the discussion of torque and energy, both of which are N*m in SI.

That discussion has to do with the failure of SI to notate the directions of vectors. When it's torque, the N and the m are at a right angle. When it's work, they are both in the same direction.

>> That discussion has to do with the failure of SI to notate the directions of vectors.

Well if radian is a unit then torque become Nm/r and is no longer Nm like energy. Then when multiplied by an angle in radians you get energy. It was *something like that*.

rad is a unit already. https://en.wikipedia.org/wiki/Rad_(unit)

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