Students begin by learning the language and applying basic postulates, definitions, and algebraic principles in the proof of simple theorems. They simultaneously learn the deductive structure, an integral part of the course. The concept of congruency is studied in triangles as students become proficient in logic and proof. The concept of parallel lines is introduced and applied in the study of the properties of special quadrilaterals. After a brief introduction to solid geometry, the proof is de-emphasized as students consider polygons and examine the concept of similarity. They then move to geometry's most elegant theorem, the Pythagorean. This topic provides an introduction to trigonometry and a review of many of the algebraic principles studied in previous years. The year concludes with the study of circles.