1, domain

cosx≠0

x≠kπ+π/2

2. Scope

|cosx|≤ 1

f(x)∈(-∞，0]

3. Monotone interval

X ∈ (2kπ]-π/2,2kπ] increasing function

X∈(2kπ, 2kπ+π/2) Subtraction Function

4. Parity

F (-x) = log2 | cos (-x) | = log2 | cosx | = f (x) even function

5. Minimum positive period

T=π