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## PowerPoint Slideshow about ' Basic Geometry' - roger

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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.”

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.

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.

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