Introduction to Geometry

2. A 3D figure with polygonal base and triangular lateral faces that meet at a single point called apex.
3. polygon. A polygon with all sides being equal.
6. polygon. A polygon with at least one of the interior angles being greater than 180°.
10. angle. An angle in 90°.
11. angle. An angle greater than 0° and less than 90°.
12. A perfectly round 3D figure where every point on its surface is equidistant from a single, central point. It looks like a ball.
17. polygon. A polygon with all sides and all interior angles being equal.
20. angle. An angle in 180°.
21. A 3D figure defined by two identical and parallel circular bases connected by a continuous curved lateral surface.
22. triangle. A triangle with one angle in 90°.
24. triangle. A triangle with all sides being unequal.
25. angle. An angle in 360°.

1. angles. Two angles whose measures add up to 180°.
4. angle. An angle greater than 90° and less than 180°.
5. angles. Two angles whose measures add up to 90°.
7. triangle. A triangle with one angle greater than 90° and less than 180°.
8. A 3D figure with a curved surface that narrows smoothly from flat, circular base to a point called vertex or apex.
9. triangle. A triangle with all sides being equal.
13. lines. Two straight lines on the same plane do not intersect no matter how far they extend.
14. polygon. A polygon with all interior angles being equal.
15. lines. Two straight lines intersect and form a right angle.
16. triangle. A triangle with all angles being greater than 0° and less than 90°.
18. triangle. A triangle with two sides being equal.
19. polygon. A polygon with all interior angles being less than 180°.
22. angle. An angle greater than 180° and less than 360°.
23. A 3D figure with two ends in the same shape.