SOLUTION: I'm stuck on how to solve this. Cos(theta) + sin(theta) = 0

        cos(Ɵ) + sin(Ɵ) = 0

                 sin(Ɵ) = -cos(Ɵ)

Divide both sides by cos(Ɵ)
                       
                    = 

                 tan(Ɵ) = -1

The tangent is negative in quadrants II and IV.  If all you want are 
the angles Ɵ between 0 and 360°, they are 135° and 315°. Or if in 
radians then  and . 

However if you want the general solution:


                      Ɵ = angles in quadrants II and IV which have reference
                          angles 45°, or 

                      Ɵ = 135° + 180°n      if in degrees

                      Ɵ =             if in radians.

                      where n can be any integer, positive, negative or zero. 

Edwin