** Lesson's Content **

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** Lesson's Glossary **

**Acute triangle
A triangle whose angles are acute.**

**Angle
Geometry shape formed by two rays (initial and ending sides of the angle) that share a common endpoint called the vertex. You may name an angle using the vertex, or a point in each ray and the vertex label in the center.**

** Angle-angle-side (AAS) congruence states that if any two consecutive angles of a triangle are equal in measure to two consecutive angles of another triangle and a pair of corresponding not included sides to these angles is congruent; then the two triangles are congruent; that is, they have exactly the same shape and size.**

**Angle-side-angle (ASA) congruence states that if any two angles of a triangle are equal in measure to two angles of another triangle and the side in between each pair of angles have the same length, then the two triangles are congruent; that is, they have exactly the same shape and size.**

**Concave polygon
If a polygon has diagonals that lie outside the polygon then the polygon is concave.**

** Convex polygon
A convex polygon is any polygon that is not concave.**

**Equilateral triangle
A triangle whose sides are equal in length.**

**Included angle
The angle made by two sides of a polygon .**

**Included side
The side between two consecutive angles in a polygon.**

**Isosceles trapezoid
Trapezoid with two non-congruent and non-parallel sides.**

**Isosceles triangle
A triangle with two sides of equal length.**

**Kite
Parallelogram with two pairs of adjacent sides congruent and without opposite sides congruent.**

**Parallelogram
Any quadrilateral with two pairs of opposite sides parallel.**

**Polygon
It is a closed plane figure with a least three straight segments as sides.**

**Quadrilateral
A four-sided polygon.**

**Rectangle
Any parallelogram that has 4 right angles.**

**Rhombus
Any parallelogram with 4 congruent sides.**

**Right triangle
A triangle that has a 90 degree angle.**

**Scalene triangle
A triangle with no equilateral sides.**

**Side-angle-side (SAS) congruence states that if any two sides of a triangle are equal in length to two sides of another triangle and the angles between each pair of sides have the same measure, then the two triangles are congruent; that is, they have exactly the same shape and size.
Side-side-side (SSS) congruence states that if the three sides of one triangle have the same lengths as the three sides of another triangle, then the two triangles are congruent.**

**Square
Parallelogram with four congruent sides and four congruent angles.**

**Theorem
A theorem in mathematics is a proven fact. A theorem about polygon must be true for every polygon; there can be no exceptions. An idea which works in several different cases is not enough.**

**Trapezoid
Quadrilateral with exactly one pair of parallel sides.**

**Vertex of a polygon (plural vertices)
An endpoint of a segment in a polygon.**

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