Using Excel and substituting "N" in place of "13", I note that:
The first term only shows equality for "3".
ie tan(pi/3) = 3^(1/2).
The product of the first 2 terms shows equality for N=5.
The product of the first 3 terms shows equality for N=7.
The product of the first 4 terms shows equality for N=9.
The product of the first 5 terms shows equality for N=11.
The product of the first 6 terms shows equality for N=13.
The product of the first 7 terms shows equality for N=15.
So far, I have no idea why

Posted by Larry
on 20140817 10:20:09 