Unit 1 - Foundations of Geometry Vocabulary

Circle

• A round plane figure whose boundary consists of points equidistant from the center.

• A polygon with three sides and three angles.

• A closed figure with four equal sides and angles.

• A straight line that connects two points in a plane.

Acute Angle

• An angle that is less than 90 degrees.

• An angle that is exactly 90 degrees.

• An angle that is greater than 90 degrees but less than 180 degrees.

• An angle that is equal to 180 degrees.

Right Angle

• An angle that is exactly 90 degrees.

• An angle that is less than 90 degrees.

• An angle that is greater than 90 degrees but less than 180 degrees.

• An angle that is exactly 180 degrees.

Linear Pairs

• A pair of adjacent angles formed when two lines intersect.

• A pair of angles that are opposite each other when two lines intersect.

• A pair of angles that add up to 90 degrees.

• A pair of angles that are complementary but not adjacent.

Angle Addition Postulate

• If a point lies in the interior of an angle, the sum of the two smaller angles is equal to the larger angle.

• The sum of the angles in a triangle is always 180 degrees.

• An exterior angle is equal to the sum of the two opposite interior angles.

• The angles opposite to equal sides of a triangle are equal.

Congruent

• Having the same size and shape.

• Having different sizes but similar shapes.

• Having the same area but different shapes.

• Having no relation in size or shape.

Radicand

• The number or expression inside a radical symbol.

• A type of mathematical operation involving addition.

• A term used to describe the square root of a number.

• A symbol used to denote multiplication.

Coplanar Points

• Points that lie on the same plane.

• Points that lie on different planes.

• Points that are collinear.

• Points that form a triangle.

Parallel Lines

• Lines that intersect at a single point.

• Lines in a plane that do not meet; they are always the same distance apart.

• Lines that are perpendicular to each other.

• Lines that curve away from each other.

Segment Addition Postulate

• If a point B lies on a line segment AC, then AB + BC = AC.

• If a point B lies outside a line segment AC, then AB + BC = AC.

• If a point B lies on a line segment AC, then AB - BC = AC.

• If a point B lies on a line segment AC, then AB + AC = BC.