The trigonometric equation is .

Devide each side by  .

The function tan A  has period of 2π , first find all solutions in the interval [ 0 , 2 π ] .

The function tan A is positive in first and third quadrants.

In first quadrant : \ \

.

In third quadrant :

.

The function tan A is negative in second and fourth quadrants

In second quadrant :

In fourth quadrant :

The solutions are in the interval [ 0 , 2 π ].