#### cephas1012

**Registered Senior Member**

1. Is there a trig identity for Sin[x/3] where Sin[x] is known? If so what is it? I am pretty sure I have heard there isnt one...but I could be wrong.

2. This question is a little harder for me to describe. Suppose you start with 1 and say that you can add it together as many times as you like and that you may also add 1*1/2^n together as many times as you like for an integer value of n. So in other words you could get values like 5,4,3/2, 1/2, 1/8, etc. Is there a proof that you can get all rational numbers from this process, or a proof that you cannot? I am really curious about it.

thanks