It depends on what you mean by "what can be used", you can use a protractor or ruler since it's a line segment. OR you can use the formula a^ + b^ = c^ to find out all the measurements.......
If you still can't find it, then, you can try to find the other measurements around that specific line segments. And it DEPENDS on what you choose to find the length of this segment.
( There's no picture on my screen, so I'm guessing that you didn't put any.. )
Well, I hope this can help you :3
STAY SAFE!! :)