How does inTangent and outTangent in a KeyFrame work?

Questions & Answers
1

I have trouble understanding the math behind tangent values in KeyFrame structs. How do they work exactly?

The documentation is not much help:
http://unity3d.com/support/documentation/ScriptReference/Keyframe-inTangent.html

2

Aha!
http://clem.mscd.edu/~talmanl/HTML/TangentCurve.html

Given that ‘key’ is the type of KeyFrame:

key.outTanget represents the direction from ( key.time, key.value ) towards ( key.time+1, key.outTangent )

key.inTanget represents the direction from ( key.time, key.value ) towards ( key.time-1, -key.inTangent )