0 to 360°
It is probably hard to picture an angle of 0°, but they do exist. Imagine two rays that are collapsed together so really, it looks just like one ray. That is a 0° angle. As you learned a couple of pages ago, 360° is a circle. Then, you have 359 possibilities left. Let’s take a look at some.
Right Angles
Shaped like an L, the 90° right angle is easy to identify. Think back to perpendicular lines. Yep, that is a right angle.
Acute, Obtuse, and Reflex Angles
These three angles are easy to identify. The key degrees are 90 and 180. Acute angles are less than 90°, while obtuse angles are greater than 90°, but less than 180°. A reflex angle is greater than 180°. You can identify the reflex angle by one of the angles pointing downward.
Adjacent Angles
Adjacent angles will have at least three lines involved. They are considered adjacent because the angles share a common side. For example, we have two angles (A and B) below due to the line in the middle.
Complementary and Supplementary Angles
To identify the difference between complementary and supplementary angles, the key degrees are 90 and 180. When adjacent angles add up to 90°, they are complementary. Adjacent angles that sum 180° are supplementary.
Vertical Angles
Two intersecting lines form four angles. The angles opposite each other are called vertical angles. Vertical angles are equal. Also, look at it this way: each side forms a supplemental angle. A and B are vertical angles as are C and D. You can see supplemental angles in:A and C, A and D, B and D, C and D. Each of the supplemental combos equal 180° .
Corresponding Angles
Two angles sharing the same relative position and equal are corresponding angles. The common example is parallel lines with a third line cutting through them at an angle. The third line is also known as the transversal. Do you see the vertical and supplemental angles too?
