(115) the product of integers x, y, and z is even. is z even?

1. X/Y = Z

if x = 6, y = 2, then z = 3, not even

if x = 6, y = 3, then z = 2, even

2. Z=XY 

so (z)^2 = 2*k (because x*y*z = 2k, where k is an integer)

Sufficient, as if square of an integer is even ,then the integer is even

Sin(a)+cos(a)+cot(a)-1=2(csc(x)+1)