Hello, I have a hard time figuring out where to start for this problem:
If prove that
From given, we know . Now we consider 2 cases for this proof:
(1) If , the prove is trivial.
(2) Now let's consider the case and . By a simply manipulation, we found that showing is equivalent to showing . Now let's start from the only given identity and see what we can get.
Also realize that
Combine and , we have
and , multiply these two identities gives us .
Roy