Tough Trigonometric Function Graph Problem

Thanks Alan, ... but it doesn't help me.   

I graphed it too, but I have no idea how to answer the question.    

Calculate sin(sin(X)).  Plot this point on the graph.  Draw a horizontal line from -10pi to 10pi at this level. 

Now calculate sin(sin(Y)).  All we know is that it must be on the same horizontal line as well as on the curve.

There are 20 possible values of sin(sin(Y)) that are the same as sin(sin(X)).  

Hence the probability that X = Y is 1/20.

(At least, I think that's the interpretation of this question!).

Thanks Alan,

I still don't get it but it doesn't matter.