Solutions will be when and when .
HOWEVER if , this implies which is invalid.
So the only solutions are found by solving (because if then so does )
Hint: . Now use either the known period of or the symmetry of the unit circle to find the second value of .
You're expected to know these things. If you don't, then you should be reviewing earlier work on how to solve basic trig equations involving sin, cos and tan instead of attempting to solve the equations you've been posting.