Geometry Unit 3

  • Right Triangle — A triangle with one 90° angle.

  • Leg — Either of the two sides that form the right angle.

  • Hypotenuse — The side opposite the 90° angle; always the longest side.

  • Pythagorean Triple — Three whole numbers that satisfy a2+b2=c2.

  • Congruent Right Triangles — Right triangles that are the same size and shape.

  • HL (Hypotenuse-Leg) — A right-triangle congruence shortcut using the hypotenuse and one leg.

  • LL (Leg-Leg) — A right-triangle congruence shortcut using both legs.

  • LA (Leg-Angle) — A right-triangle congruence shortcut using a leg and an acute angle.

  • HA (Hypotenuse-Angle) — A right-triangle congruence shortcut using the hypotenuse and an acute angle.

  • Angle Bisector — A line, ray, or segment that divides an angle into two congruent angles.

  • Perpendicular Bisector — A line that cuts a segment at its midpoint and at a 90° angle.

  • Similar Triangles — Triangles with the same shape; corresponding angles are congruent and sides are proportional.

  • AA Similarity — Two triangles are similar if two pairs of corresponding angles are congruent.

  • Altitude — A perpendicular segment from a vertex to the opposite side or its extension.

  • Hypotenuse Segments — The two parts of the hypotenuse created when an altitude is drawn to it.

  • Geometric Mean — The positive number x such that a/x=x/b, so x=ab​.

  • 45°-45°-90° Triangle — A right triangle with two 45° angles and congruent legs.

  • 30°-60°-90° Triangle — A right triangle with angles of 30°, 60°, and 90°.

  • Special Right Triangle — A right triangle with predictable side-length relationships.

  • Right Triangle Altitude Theorem — Drawing an altitude to the hypotenuse creates two smaller triangles similar to the original triangle.