It is equivalent to dividing the whole quadrant into 8 parts, and each quadrant has 2 parts.

A is in the second quadrant, a∈( 1/4, 1/2)

2a∈( 1/2, 1) three quadrants.

A/2∈( 1/8, 1/4) a quadrant.

2a belongs to two quadrants, namely 2A ∈ (1/4, 1/2) A ∈ (1/8, 1/4).

A/2∑( 1/4, 1/2)A∑( 1/2, 1) three quadrants.