Download Topic 11 Geometry Terms

Topic 11 Geometry Terms
Lesson 1
Point – an exact position
Line – a set of points that is endless in two directions
Line segment – a part of a line with two endpoints
Intersecting lines cross at one point
Parallel lines never cross.
Lesson 2
Ray – a part of a line with one endpoint
Angle – formed by two rays with the same endpoint
Vertex – the endpoint on an angle
Right angle – makes a square corner
Perpendicular – the two lines, line segments, or rays that make a right angle
Acute angle – angle that is open less than a right angle
Obtuse angle – angle that is open more than a right angle
Lesson 3
Polygon – a closed shape made up of line segments. Each line segment is a
side of the polygon. Where the two sides meet is the vertex.
Diagonal – a line segment that connects two vertices that are not next to
each other.
Triangle – 3 sides and vertices
Quadrilateral – 4 sides and vertices
Pentagon – 5 sides and vertices
Hexagon – 6 sides and vertices
Octagon – 8 sides and vertices
Decagon – 10 sides and vertices
Concave polygons – one or more angles move in towards the center of the
polygon.
Convex polygons – all the angles move out away from the center.
Lesson 4
A triangle can be named by its sides or by its angles. Triangles can have more than
one name.
Equilateral triangle – All three sides are the same length.
Isosceles triangle – At least two sides are the same length.
Scalene triangle – No sides are the same length.
Right triangle – One angle is a right angle.
Acute triangle – All three angles are acute angles.
Obtuse triangle – One angle is an obtuse angle.
Lesson 5
Some quadrilaterals have more than one special name. The following
are all special parallelograms.
Rectangle – four right angles, a special par
Rhombus - all sides the same length
Square – four right angles and all the sides the same length
Some other special quadrilaterals are:
Trapezoid – exactly one pair of parallel sides
Parallelogram – two pairs of parallel sides. Opposite sides are the same
length. Opposite angles are the same size.
The rest of the lessons will involve problem solving with these polygons,
lines, and angles.