Geometry: Angles 1 to 19 Explained
1. Angle: Formed when two rays (or line segments) meet at a common endpoint (vertex).
2. Types of angles: Includes various kinds such as acute, obtuse, right, etc., based on their
measure.
3. Acute angle: An angle less than 90°.
4. Obtuse angle: An angle greater than 90° but less than 180°.
5. Right angle: An angle exactly equal to 90°.
6. Straight angle: An angle exactly equal to 180°.
7. Reflex angle: An angle greater than 180° but less than 360°.
8. Complete angle: An angle equal to 360°.
9. Zero angle: An angle that measures 0°.
10. Corresponding angles: Angles in matching corners when two lines are crossed by
another line (transversal).
11. Alternate interior angles: Angles on opposite sides of the transversal but inside the
two lines.
12. Alternate exterior angles: Angles on opposite sides of the transversal and outside the
two lines.
13. Co-interior angles: Angles on the same side of the transversal and inside the two lines;
also called consecutive interior angles.
14. Co-exterior angles: Angles on the same side of the transversal and outside the two
lines.
15. Vertically opposite angles: Angles formed opposite each other when two lines
intersect; they are equal.
16. Complementary angles: Two angles whose measures add up to 90°.
17. Supplementary angles: Two angles whose measures add up to 180°.
18. Adjacent angles: Angles that have a common side and a common vertex, and don’t
overlap.
19. Linear pair: A pair of adjacent angles whose non-common sides form a straight line
(180°).