We can substitute a=pi/4 into the expression:

1 + cos(2(pi/4)) / (1 - cos(2(pi/4))
= 1 + cos(pi/2) / (1 - cos(pi/2))
= 1 + 0 / (1 + 0)
= 1

Therefore, the value of the expression is 1 when a = pi/4.