Core 2 question on Radians

Can someone translate for me what this question is asking, I just cant get my head aroud it
The question is in attachments and the cut off circle is for the next question.

which bit confuses you?

The "Subtends an angle of theta" bit

I'm going to have to kindly request that if you post your problem on another thread, it's a little selfish of you to make a new thread for it, because you might make two different people answer you, which is a waste of effort on their part. Try sticking to either posting it in the existing thread or only creating a new thread - you could put a link from the existing thread to the new one, if you'd like.