# ONE MATHEMATICAL CAT, PLEASE! Topics in Geometry

These lessons use MathJax to get the beautiful mathematics. Enjoy!

 1 Beginning Terminology, Points, Lines, and Planes 2 Segments, Rays, Angles 3 Introduction to Polygons 4 Interior and Exterior Angles in Polygons 5 Quadrilaterals 6 ‘If ... Then ...’ Sentences 7 Contrapositive and Converse 8 Proof Techniques 9 Logical Equivalences and Practice with Truth Tables 10 Applying Logical Equivalences to Algebraic and Geometric Statements 11 Constructions 12 Introduction to the Two-Column Proof 13 The Pythagorean Theorem 14 More Terminology for Segments and Angles 15 Angles: Complementary, Supplementary, Vertical, and Linear Pairs 16 Equivalence Relations 17 Triangle Congruence 18 Relationships between Angles and Sides in Triangles 19 Practice with Two-Column Proofs 20 Is there an ‘SSA’ Congruence Theorem? No! 21 More on Exterior Angles in Triangles 22 Parallel Lines 23 Parallelograms and Negating Sentences 24 Introduction to Area and Perimeter 25 Area Formulas: Triangle, Parallelogram, Trapezoid 26 Similarity, Ratios, and Proportions 27 Perimeters and Areas of Similar Polygons 28 Two Special Triangles