Divide through by 





Use the identity 
to replace the left side:



Add -3 to both sides



Divide both sides by 4



There are two quadrants in which
the tangent is negative, QII and QIV

They are these two angles:

 and this  

Now we find the reference angle of these two
angles by calculator using inverse tangent
and POSITIVE 

°

The angle in the second quadrant is found
by subtracting the reference angle from 180°

180° - 36.86989765° = 143.1301025°

The angle in the fourth quadrant is found
by subtracting the reference angle from 360°

360° - 36.86989765° = 323.1301025°

Edwin