# complementary angles

• Jul 16th 2010, 06:18 AM
Kat-M
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?
• Jul 16th 2010, 06:24 AM
Prove It
When dealing with complementary angles, it's actually their magnitudes (sizes) that have to add to $90^\circ$.
• Jul 16th 2010, 06:27 AM
Kat-M
Quote:

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?
• Jul 16th 2010, 06:27 PM
Prove It
Yes. If you were to draw both on the unit circle, you would have a $90^{\circ}$ angle.