What is the length of the Keyframe tangent?

Hi guys

I'm trying to make sense of the AnimationCurve and KeyFrame objects.

I've been able to figure out the in/out tangent angles, but I'm not sure how Unity assigns lengths to the tangents.

I had hoped I could simply take 1/3 of the length of the line from the current Keyframe to the next, but this doesn't seem to be correct:

AnimationCurve editor window (goes from 0,0 to 1,1 - the aspect ratio is just weird)

My reconstruction

The co-ordinates and tangent angles are all correct, the problem however is the shape of the curve.

Does anyone know what length Unity assigns to Keyframe tangents? Or perhaps it's some function of the angle?

Thanks, Ves