1. ## complementary angles

two angles are called complementary angles if they add up to 90 degrees, right?
then what about 110 and -20? are they complementary? or complementary angles have to be both positive?

2. When dealing with complementary angles, it's actually their magnitudes (sizes) that have to add to $90^\circ$.

3. Originally Posted by Prove It
When dealing with complementary angles, it's actually their magnitudes (sizes) that have to add to $90^\circ$.
so does that mean 30 and -60 are complementary?

4. Yes. If you were to draw both on the unit circle, you would have a $90^{\circ}$ angle.