∴2θ=2kπ+π/2 (k∈Z)

∴θ=kπ+π/4

When k is odd, cosθ=-√2/2.

Do not meet the second condition, give up.

When k is an even number, cosθ=√2/2.

The second condition is met,

Therefore,

θ=2mπ+π/4 (m∈Z)