basic geometry vocabulary review. plane and solid figures plane figure – a plane figure has just 2...
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Basic Geometry
Vocabulary Review
Plane and Solid Figures
• Plane figure – a plane figure has just 2 dimensions – length and width.
• Solid figure – a solid figure has 3 dimensions – length, width, and height.
Solid Figures
• Face – each flat surface of a solid figure
• Edge – a line segment where 2 faces meet on a solid figure.
• Vertex – “a corner” – where 3 or more edges meet. The plural form of vertex is “vertices.”
Solid Figures
Polygons
• Polygon – a polygon is a closed plane figure made up of line segments. Each line segment is a side.
Polygons – Know Your Prefixes!• “Tri” – means 3 – a triangle has 3
sides.• “Quad” – means 4 – a
quadrilateral has 4 sides.• “Penta” – means 5 – a pentagon
has 5 sides.• “Hexa” – means 6 – a hexagon
has 6 sides.• “Octa” – means 8 – an octagon
has 8 sides.• “Nona” – means 9 – a nonagon
has 9 sides.• “Deca” – means 10 – a decagon
has ten sides.
Points, Lines, Line Segments, and Rays
• Point – an exact location in space.
• Line – a straight path of points that goes on and on in two directions.
• Line segment – a part of a line. It has 2 endpoints.
• Ray – part of a line. It has one endpoint and continues on and on in only one direction.
Angles• Right angle – has a
square corner
• Acute angle – less than a right angle
• Obtuse angle – more than a right angle.
• Straight angle – forms a straight line.
Lines
• Parallel lines – never intersect.
• Intersecting lines – lines that cross through the same point.
• Perpendicular lines – lines that form right angles where they intersect each other.
Triangles
• We learned that there are 2 ways to classify (or group) triangles.
• One way is to classify (or group) triangles by the length of their sides.
• The second way is to classify (or group) them is by their angles.
• Length of sides – Equilateral, isosceles, or scalene.
• By their angles – right, acute, or obtuse.
Equilateral Triangles
• Equilateral triangles – all 3 sides have the same length.
Isosceles Triangle
• Isosceles triangle – 2 of the sides have the same length. You can see that the base (or bottom) of the triangle is shorter than the 2 sides. However, the 2 sides are the same length.
Scalene Triangle
• Scalene triangle – none of the 3 sides are the same length.
Right Triangle
• Right Triangle – 1 angle of the triangle is a right angle.
Acute Triangle
• Acute triangle – all 3 angles of the triangle are acute angles.
• Remember – if all 3 sides are the same length (equilateral), the triangle is automatically an acute triangle!
Obtuse Triangle
• Obtuse triangle – if one of the angles of the triangle makes an obtuse angle, the triangle is an obtuse triangle.
Quadrilaterals
• Quadrilaterals can also be classified (or grouped) by their angles or their pairs of sides!
• Remember , quad means 4! So we are talking about 4 sided figures!
Rectangle
• Rectangle – there are 4 right angles!
Square
• Square – there are 4 right angles and all sides are the same length.
Trapezoid
• Trapezoid – There is only one pair of parallel sides.
Parallelogram
• Parallelogram – opposite sides are parallel.
Rhombus
• Rhombus – opposite sides are parallel AND all 4 sides are the same length.
Circles
• Circles – we learned that circles are different from other plane figures because they have no sides.
• A circles is a closed plane figure made of all the points in the same distance from a point called the center.
Center of the Circle
Radius
• Radius – is any line that segment that connects the center to a point on the circle.
Diameter
• Diameter – is any line segment that connects two points on the circle and passes through the center.
Chord
• Chord – is any line segment that connects two points on a circle.
Circumference of a Circle
• Circumference – the distance around the outside of a circle.
• The circumference of a circle is calculated by multiplying pi (3.14) times the diameter of the circle.
Congruent
• Congruent – same shape, same size.
Slide (Translation)
• Slide (translation) – moves a figure in a straight direction.
Flip (Reflection)
• Flip (reflection) – a figure gives its mirror image.
Turn (Rotation)
• Turn (rotation) – moves a figure around a point.
Symmetry
• Symmetry – when a figure can be folded into two congruent halves. *Means one half can lay perfectly over the other half in an exact match.
line of symmetry
Similar
• Similar – same shape, but may or may not have the same size! *If items are congruent, they are automatically similar. However, just because items are similar, doesn’t mean they are automatically congruent.
Perimeter
• Perimeter – the distance around the outside of a figure.
• Just add the length of all sides together to calculate the perimeter.
• Real world use of perimeter – building a fence.
Area
• Area – the number of square units needed to cover the region inside a figure.
• Multiply the length x width to find the area of a figure.
• Real world use of area – flooring/carpet.
• Remember – use “square” in your answer. 32 sq. in.
Volume
• Volume – the number of CUBIC units needed to fill a solid figure.
• Multiply the length x width x height to calculate the volume.
• Real world of volume – Shopping for refrigerator or freezers. Shipping companies like UPS or FedEx.
• Remember to use “CUBIC” in your answer. 48 cubic inches.