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**1. The problem statement, all variables and given/known data**

I'm having a tough time with relativity, and I thought I'd try this problem to see if I understood the topic very well.

Let's consider a train moving at 0.65c along a straight track. Its headlight produces a beam with an angular spread of 60 degrees. If you astanding alongside the track (rails are 1.5 m apart), how far from you is the train when you see its approaching headlight suddenly disappear?

**2. Relevant equations**

**3. The attempt at a solution**

I drew a picture, but I really need a hint on how to get started. I'm thinking about using length contraction somehow, but I just can't get my head around what I need to do.

Here's the best I've got right now: From trigonometry I have x= tan(60)*.75, x = 1.3, and I'm pretty sure this isn't right.

Any help would be greatly appreciated.

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