Chapter 11 Geometry

triangle

a 3 sides and 3 angles

quadrilateral

a four-sided figure.

parallelogram

a four-sided plane rectilinear figure with opposite sides parallel.

pyramid

a monumental structure with a square or triangular base and sloping sides that meet in a point at the top,

rhombus

a parallelogram with opposite equal acute angles, opposite equal obtuse angles, and four equal sides.

polygon

a plane figure with at least three straight sides and angles, and typically five or more.

octagon

a plane figure with eight straight sides and eight angles.

pentagon

a plane figure with five straight sides and five angles.

square

a plane figure with four equal straight sides and four right angles.

rectangle

a plane figure with four straight sides and four right angles, especially one with unequal adjacent sides, in contrast to a square.

nonagon

a plane figure with nine straight sides and nine angles.

hexagon

a plane figure with six straight sides and angles.

decagon

a plane figure with ten straight sides and angles.

regular polygon

a polygon in which all sides and angles are congrugent

trapezoid

a quadrilateral with only one pair of parallel sides.

sphere

a round solid figure, or its surface, with every point on its surface equidistant from its center.

polyhedrons

a solid figure with faces that are polygons

cylinder

a solid geometric figure with straight parallel sides and a circular or oval cross section.

cone

a solid or hollow object that tapers from a circular or roughly circular base to a point.

acute triangle

a triangle with 2 angles less than 90 degrees

isosceles triangle

a triangle with 2 congrugent sides

equilateral triangle

a triangle with 3 congrugent sides

right triangle

a triangle with a right angle

obtuse triangle

a triangle with one obtuse angle

right angle

an angle that measures 90 degrees

congruent

identical in form; coinciding exactly when superimposed.

Hexagonal prism

the hexagonal prism is a prism with hexagonal base. This polyhedron has 8 faces, 18 edges, and 12 vertices.

angle

the point were lines meet

non-polyhedrons

three dimensional figures with curved faces

rectangular pyramid

. A rectangular pyramid has a rectangle for a base with triangles for the other faces. Sometimes the rectangle at the base is actually a square.

Heptagon

A 7-sided figure

not a regular polygon

A polygon that does not have all sides equal and all angles equal. A polygon is "regular" only when all angles are equal and all sides are equal, otherwise it is irregular

pentagonal prism

A rectangular prism is a solid figure where all sides are rectangles and all sides meet perpendicular.

rectangular prism

A rectangular prism is a solid figure where all sides are rectangles and all sides meet perpendicular.

prism

A solid figure that has two congruent, parallel polygons as its bases. Its sides are parallelograms

triangular pyramid

A triangular pyramid is a pyramid having a triangular base.

acute angle

An angle that is less than 90 degrees

obtuse angle

An angle that measures more than 90 degrees but less than 180 degrees

lateral faces

Any surface of a polyhedron other than a base

base

In 2 dimensions, one side of a triangle or parelellogram

pentagonal pyramid

In geometry, a pentagonal pyramid is a pyramid with a pentagonal base upon which are erected five triangular faces that meet at a point (the vertex). Like any pyramid, it is self-dual. The regular pentagonal pyramid has a base that is a regular pentagon and lateral faces that are equilateral triangles.

hexagonal prism

In geometry, the hexagonal prism is a prism with hexagonal base. This polyhedron has 8 faces, 18 edges, and 12 vertices.

octagonal prism

In geometry, the octagonal prism is the sixth in an infinite set of prisms, formed by square sides and two regular octagon caps. If faces are all regular, it is a semiregular polyhedron.