1.a 1, a2, a3 and a4 are the first, second, third and fourth quadrant angles respectively.

2. There are three or four quadrant angles respectively. The previous set is {a | a = 7/6 pie plus 2k pie, where k belongs to z}

The latter is {A | A = 1 1 Paijia 2k school, where k belongs to Z}

3 (1) 74 of the 45 factions MINUS two factions.

(2) The Erjiu School and the Second School.

(3)-6 faction 143 faction 72.

4. 1 1.25 degrees, 16 minute radians.

5.64 degrees