Cones and Cylinders What is a Polyhedron? The term refers to the number of faces.A square pyramid and triangular prism are both pentahedrons. Not as descriptive as prism or pyramid names.
Warm Up • Review Answers to #7 on page 386
Practical Application • Architects use a variety of 3-D figures, and combinations, or modifications of these figures in their designs. Certain figures are used in packaging because some figures require less surface area for the same amount of volume than others.
Important Terms Cone – 3-D object with a base that’s a flat surface, an apex, and ALL points on the base connect to the apex by a line segment. Right Circular Cone – Circular base and a line drawn through the apex and the centre of the base is perpendicular to the base. Apex is highest point from the base.
Oblique • If the line drawn from the apex to the base does not form a right angle, the cone is called oblique.
Describing Cones or Pyramids • Full descriptions include right or oblique as well as the name of it’s base. Ex. Egyptian pyramids are right square pyramids How would the faces of a right pentagonal pyramid be different from those of an oblique pentagonal pyryamid?
Cylinders • Cylinder is a 3-D object with parallel & congruent flat bases. ALL corresponding points on base connect by line segments along the surface.
Symmetry • Planes of Symmetry – cut the shape into two equal pieces.
Practice • Page 408 #1,2,3a,b, 5, 6 (table for prism), 8