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# Basic Geometry - PowerPoint PPT Presentation

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

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## PowerPoint Slideshow about ' Basic Geometry' - roger

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Presentation Transcript

### Basic Geometry

Vocabulary Review

• Plane figure – a plane figure has just 2 dimensions – length and width.

• Solid figure – a solid figure has 3 dimensions – length, width, and height.

• 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.”

• Polygon – a polygon is a closed plane figure made up of line segments. Each line segment is a side.

• “Tri” – means 3 – a triangle has 3 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.

• 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.

• 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.

• 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.

• 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 – all 3 sides have the same length.

• 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 – none of the 3 sides are the same length.

• Right Triangle – 1 angle of the triangle is a right angle.

• 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 – if one of the angles of the triangle makes an obtuse angle, the triangle is an obtuse triangle.

• 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 – there are 4 right angles!

• Square – there are 4 right angles and all sides are the same length.

• Trapezoid – There is only one pair of parallel sides.

• Parallelogram – opposite sides are parallel.

• Rhombus – opposite sides are parallel AND all 4 sides are the same length.

• 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.

• Radius – is any line that segment that connects the center to a point on the circle.

• Diameter – is any line segment that connects two points on the circle and passes through the center.

• Chord – is any line segment that connects two points on 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 – same shape, same size.

• Slide (translation) – moves a figure in a straight direction.

• Flip (reflection) – a figure gives its mirror image.

• Turn (rotation) – moves a figure around a point.

• 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 – 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 – 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 – 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.