The focus then shifts to . You will learn to measure them using degrees and classify them as acute, right, obtuse, or straight. This section also introduces angle pairs , such as: Complementary: Angles that add up to 90°. Supplementary: Angles that add up to 180°.
By their sides (scalene, isosceles, equilateral) and their angles. CK-12 Basic Geometry, Volume 1 of 2
CK-12 Basic Geometry, Volume 1, isn't just about memorizing formulas; it’s about learning to see patterns and prove they exist. By mastering these five pillars, you develop a toolkit for spatial reasoning that applies to art, construction, physics, and advanced mathematics. The focus then shifts to
The final stretch of Volume 1 focuses on the most stable shape in engineering: the triangle. You will explore: Supplementary: Angles that add up to 180°
Using shortcuts like SSS (Side-Side-Side) , SAS (Side-Angle-Side) , and ASA (Angle-Side-Angle) to prove that two triangles are identical in size and shape. Conclusion
Everything in geometry starts with three "undefined terms": (a location), lines (a straight path extending infinitely), and planes (a flat, 2D surface). Volume 1 teaches you how to name these elements and understand their relationships, such as collinearity (points on the same line) and coplanarity (points on the same plane). Understanding these basics is essential because they form the "DNA" of every shape you will eventually study. 2. Segments and Angles
Volume 1 dives deep into the behavior of lines that never touch () and lines that cross at 90° ( perpendicular ). A major highlight is the study of a transversal —a line that crosses two other lines. You’ll learn how to identify special angle relationships like Alternate Interior Angles and Corresponding Angles , which are the keys to proving lines are parallel. 5. Triangles: Properties and Congruence