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Chapter 12 Notes. 12.1 – Exploring Solids. A polyhedron is a solid bounded by polygons. Sides are faces , edges are line segments connecting faces, and vertices are points where the edges meet. The plural of polyhedron is polyhedra or polyhedrons.
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A polyhedron is a solid bounded by polygons. Sides are faces, edges are line segments connecting faces, and vertices are points where the edges meet. The plural of polyhedron is polyhedra or polyhedrons. A polyhedron is regular if all the faces are congruent regular polygons. A polyhedron is convex if any two points on its surface can be connected by a segment that lies entirely on the polyhedron (like with polygons) There are 5 regular polyhedra, called Platonic solids (they’re just friends). They are a (look at page 721): tetrahedron (4 triangular faces) a cube (6 square faces) octahedron (8 triangular faces) dodecahedron (12 pentagonal faces) icosahedron (20 triangular faces)
http://personal.maths.surrey.ac.uk/st/H.Bruin/image/PlatonicSolids.gifhttp://personal.maths.surrey.ac.uk/st/H.Bruin/image/PlatonicSolids.gif
Is it a polyhedron? If so, count the faces, edges, and vertices. Also say whether or not it is convex. No
Euler’s Theorem: (Like FAVE two, or cube method) Edges = Sides/2 Find vertices of polyhedra made up of 8 trapezoids, 2 squares, 4 rectangles. Find vertices of polyhedra made up of 2 hexagons, 6 squares.
The intersection of a plane crossing a solid is called a cross section. Sometimes you see it in bio, when they show you the inside of a tree, the circle you get when you slice a tree is called the cross section of a tree.
Terms P Perimeter of one base B Area of base b base (side) h Height (relating to altitude) l Slant Height TA Total Area (Also SA for surface Area) LA Lateral Area V Volume
A prism has two parallel bases. Altitude is segment perpendicular to the parallel planes, also referred to as “Height”. Lateral faces are faces that are not the bases. The parallel segments joining them are lateral edges. Prism Net View
If the lateral faces are rectangles, it is called a RIGHT PRISM. If they are not, they are called an OBLIQUE PRISM. Altitude. Lateral edge not an altitude. OBLIQUE PRISM. RIGHT PRISM
Lateral Area of a right prism is the sum of area of all the LATERAL faces. = bh + bh + bh + bh = (b + b + b + b)h = Ph LA Total Area is the sum of ALL the faces. = 2B + Ph TA
Find the LA, SA of this triangular prism. LA = SA = 8 4 3 5
Find the LA, SA of this rectangular prism. LA = SA = 5 3 8
Find the LA and TA of this regular hexagonal prism. If it helps to think like this. 10 4
Find the LA, and TA of this prism. 24 in 30 in 6 in 10 in 8 in
Find lateral area, surface area Height = 8 cm Radius = 4 cm Height = 2 cm Radius = .25 cm
Find the Unknown Variable. SA = x 2 8 V = 2x x 4
Find the Unknown Variable. SA = 40πcm2 Radius = 4 cm Height = h SA = 100πcm2 Radius = r Height = 4 cm
vertex Lateral edge Altitude (height) Slant height Lateral Face (yellow) Base (light blue)
A regular pyramid has a regular polygon for a base and its height meets the base at its center.
Lateral Area of a regular pyramid is the area of all the LATERAL faces. Total area is area of bases. TA = B + Pl b b b b b + + + + l l l l l (b b b b b) + + + + =Pl l
Find Lateral Area, Total Area of regular hexagonal pyramid. 10 in 16 in
Find Lateral Area, Total Area of regular square pyramid. 13 cm 10 cm
Find lateral area, surface area Find surface area. Units in meters. 6 8 Slant Height = 15 in. Radius = 9 in
Find unknown variable 8 cm x cm Slant height 8 cm Radius = ? TA = 105cm2 Slant height 8 in Radius = ? TA = 48 πin2
Pyramid height 8 in Slant height 2 cm 20 in 2 cm 12 in
Altitude is segment perpendicular to the parallel planes, also referred to as “Height”. Volume of a right prism equals the area of the base times the height of the prism. = Bh V Prism
The volume of an OBLIQUE PRISMis also Bh, remember, it’s h, not lateral edge Altitude. Lateral edge not an altitude. OBLIQUE PRISM. RIGHT PRISM
Find the V of this triangular prism. V = 8 4 3 5
Find Volume Height = 8 cm Radius = 4 cm Cylinder
Circumference of a cylinder is 12π, and the height is 10, find the volume.
What is the volume of the solid below? Prism below is a cube.
Cone 13 cm 10 cm Slant Height = 15 in. Radius = 9 in
Circumference of a cone is 12π, and the slant height is 10, find the volume.