Need help with Principle angles

Determine the priniciple angle

-187

410

-67

905

-282

-730

135

1249

I know the answers but i am not sure how to get those answers because sometime they add or subtract 360 and sometime they add 180

Can somebody plz explain me how to get principle angle

Thanks

and 2 more question

Evaluate y = cos (theta) for 0 degree less than or equal to (Theta) less than or equal to 540 degree when y =-7 (answer to nearest degree)

Evaluate y = sin (theta) for -90 degree less than or equal to (Theta) less than or equal to 540 degree when y =-0.3 (answer to nearest degree)