The document defines and describes several different types of angles: - An acute angle measures less than 90 degrees - A right angle measures exactly 90 degrees - An obtuse angle measures more than 90 degrees - Two angles whose measures sum to 90 degrees are complementary - Two angles whose measures sum to 180 degrees are supplementary The document also lists several references used as sources for the information on angles in nature.

1. Angles in NATURE By Blaire Stillwell

2. An angle with a measure of less than 90 degrees

3. An angle with a measure of exactly 90 degrees

4. An angles with a measure of more than 90 degrees

5. Two angles whose sum equals 90 degrees.

6. Two angles whose sum equals 180 degrees

7. An angle that is cut into two congruent angles by a bisector

8. Two non-adjacent angles formed by two intersecting lines

9. Two angles that are adjacent and whose non common sides form opposite rays. The sum of the angles equals 180 degrees

10. Two rays that share a common endpoint and are determined by choosing a point on a line.