Geometric Shapes and Names |
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Join Our Geometry Teacher Community Today! http://geometrycoach.com/Geometry-Lesson-Plans/?pa=MOOMOOMATH In this video you will learn about common Geometric Shapes All about shapes Let’s take a look at many of the geometric shapes you will encounter in geometry classes. We will begin with 2d shapes which have length and width, but no height. 2d shapes include polygons and curved shapes. 3d shapes have height, width, and depth. These shapes can have straight lines or curves. Let’s get started by looking at our first type of 2d shapes “polygons” Polygons are 2-dimensional closed shapes. A closed shape does not have any openings, and all of the lines connect. You can’t leave the inside of a closed shape without crossing a line. Polygons have straight lines and do not have curves A polygon has three parts. Straight Lines Vertices which are the point at which the lines intercept Angles are formed by intercepting lines There are several types of polygons A regular polygon has equal lines and angles An irregular does not have equals lines and angles A concave polygon has one angle greater than 180 degrees A convex polygon does not have any internal angles greater than 180 degrees A simple polygon does not have any lines that cross over. A complex polygon has at least one line that crosses over itself Polygon names Named after the number of sides and angles Triangle 3 sides Quadrilateral Pentagon 5 Hexagon 6 Heptagon 7 Octagon 8 Nonagon 9 Decagon 10 Hendecagon 11 Dodecagon 12 After 12 sides it is acceptable to give the number of sides and then gon For example 14 gon has 14 sides Curved 2d shapes have curved lines instead of straight lines. Common examples of curved shapes include a circle, an ellipse which looks like a circle that has been stretched or squashed A crescent is also a curved 2d shape 3d shapes are shapes that have height, width and depth A sphere and a cone are examples of 3d shapes Many 3d shapes are considered polyhedrons. Let’s take a look at the properties of polyhedrons A polyhedron is a 3D solid figure in which each side is a flat surface composed of polygons. What is a polyhedron? A polyhedran is a 3D solid figure with a flat surface. A polyhedran does not have any curved surfaces. Polyhedron is derived from poly=many. Hedron = Face so it means many faced geometric shape. Is a Dodacahedron a polyhedron yes Is a triangle a polyhedron? No is is only 2D Is a sphere a polyhedron? No it has curves Is a coffee mug a polyhedron? No Some common examples of polyhedron are prisms and pyramids Euler's Polyhedron states that the number of faces + number of vertices = number of edges + 2 A platonic solid is a convex Polyhedron that satisfy these three characteristics All are regular polygons All faces are congruent All corners are congruent. The same number of faces meet at every vertex 3 Platonic solids are made of equilateral triangles tetrahedron, octahedron, icosahedron One platonic solid is made of squares One platonic solid is made of pentagons Cube 3 squares at each corner 6 square faces Tetrahedron 3 equilateral triangles at each corner 4 triangle faces Octahedron 4 equilateral triangles at each corner 8 triangle faces Icosahedron 5 equilateral triangles at each corner 20 triangle faces Dodecahedron 3 pentagons at each corner 12 pentagon faces -~-~~-~~~-~~-~- Please watch: "Study Skills Teacher's Secret Guide to your Best Grades" https://www.youtube.com/watch?v=f3bsg8gaSbw -~-~~-~~~-~~-~- |