Circle line-segment collision detection algorithm?

Question

I have a line from A to B and a circle positioned at C with the radius R.

What is a good alg

Answer 1

No one seems to consider projection, am I completely off track here?

Project the vector AC onto AB. The projected vector, AD, gives the new point D.
If the distance between D and C is smaller than (or equal to) R we have an intersection.

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