# Lesson 12-3, 4, 13-1 Cylinders & Prisms.

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Lesson 12-3, 4, 13-1 Cylinders & Prisms

Objectives Find lateral areas of cylinders
Find surface areas of cylinders Find volume of cylinders Find lateral areas of prisms Find surface areas of prisms Find the volume of prisms

Vocabulary Axis of a Cylinder – the segment with endpoints that are centers of circular bases Right Cylinder – A cylinder where the axis is also an altitude Oblique Cylinder – a non-right cylinder Bases – congruent faces in parallel planes Lateral faces – rectangular faces that are not bases (not all parallel) Lateral edges – intersection of lateral faces Right Prisms – a prism with lateral edges that are also altitudes Oblique Prisms – a non-right prism Lateral Area – is the sum of the areas of the lateral faces

Cylinders – Surface Area & Volume
r – radius h – height Net h h r C Volume (V) = B * h Base Area (B) = π * r2 V = π * r2 * h Surface Area = Lateral Area + Base(s) Area LA = 2π • r • h = circumference * h Bases Area = 2 • π • r2 SA = LA + BA SA = 2π • r • h + 2π • r² = 2πr (r + h)

Example 1 12 3 Find the surface area and the volume of the cylinder to the right SA = 2πrh + 2πr2  need to find r and h SA = 2πrh + 2πr2 = 2π(3)(12) + 2π(3)² = 72π + 18π = 90π = V= Bh = V = πr² h  need to find r and h V= π(r)²h = 9π(12) = 108π =

Example 2 8 Find the surface area and the volume of the cylinder to the right 14 SA = 2πrh + 2πr2  need to find r and h SA = 2πrh + 2πr2 = 2π(4)(14) + 2π(4)² = 112π + 32π = 144π = V= Bh = V = πr² h  need to find r and h V= π(r)²h = 16π(14) = 224π =

Prisms – Areas & Volumes
Regular Triangular Prism l Net LA = 3 • b • l = Perimeter • l Bases Area = 2 • ½ • b • h SA = LA + BA SA = 3 • b • l + b • h b h b b b base perimeter Surface Area (SA) – Sum of each area of (all) the faces of the solid Lateral Area (LA) – Sum of each area of the non-base(s) faces of the solid Surface Area = Lateral Area + Base(s) Area Rectangular Prism LA = 2 • w • h + 2 • L • h Bases Area = 2 • L • w SA = LA + BA SA = 2(Lw + Lh + wh) Volume (V) = B • h Base Area (B) = L • w V = L • w • h h w L

Example 1 Find the surface area and the volume of the cube to the right 8 SA = LA + BA LA = 4· w · l = Perimeter · l and Bases Area = 2 · w h SA = 4 · w · l + 2 w · h h = l = w = 8 SA = 4(8)(8) + 2(8)(8) = = square units V = B l = w h l V = (8)(8)(8) = 512 cubic units

Example 2 10 4 Find the surface area and the volume of the rectangular prism to the right 6 SA = LA + BA LA = 2(w+h) · l = Perimeter · l and Bases Area = 2 · w h SA = 2(w · h) + 2(h · l ) + 2 (w · h) h = 6, l = 10 and w = 4 SA = 2(4)(10) + 2(6)(10) + 2(4)(6) = = square units V = B l = w h l V = (4)(6)(10) = 240 cubic units

Example 3 Find the surface area and the volume of the isosceles triangle prism to the right c c 4 15 6 SA = LA + BA LA = 2 · c · l + 6 · l = Perimeter · l and Bases Area = 2 · (½ b h) SA = 2 · c · l + 6 · l + b · h b = 6, l = and use Pythagorean theorem to find c c² = 3² + 4² c = 5 SA = 2(5)(15) + 6(15) + (6)(4) = = square units V = B l = ½ b h l where h is the height of the triangular base! V = ½ (6)(4)(15) = 180 cubic units

Find the surface area of the cylinder.
The radius of the base and the height of the cylinder are given. Substitute these values in the formula to find the surface area. Surface area of a cylinder Use a calculator. Answer: The surface area is approximately sq ft. Example 4-2a

Find the volume of the cylinder to the nearest tenth.
The height h is 1.8 cm, and the radius r is 1.8 cm. Volume of a cylinder r 1.8, h 1.8 Use a calculator. Answer: The volume is approximately 18.3 cubic cm. Example 1-3a

Find the surface area of the triangular prism.
SA = 2B + LA S.A. of a prism B = ½ b h Base area = area of ∆ B = ½ (12) (8) ∆b=12, ∆h=8 B = Simplify LA = Ph P = c c² = 8² + 6² = = 100 c = 10 Pythagorean Thrm P = = 32 LA = Ph = 32 (10) = 320 SA = 2B + LA = 2 (48) = 416 Answer: 416 units2 Example 3-2c

Find the volume of the triangular prism.
V Bh Volume of a prism 1500 Simplify. Answer: The volume of the prism is 1500 cubic centimeters. Example 1-1a

Summary & Homework Summary: Homework:
Lateral surface area (LA) is the area of the sides Base surface area (B) is the area of the top/bottom Surface area = Lateral Area + Base(s) Area Prism Volume: V = Bh Surface Area: SA = LA + 2B Triangular and Rectangular prisms on formula sheet Cylinder Volume: V= πr² h Surface Area: SA = 2πrh + 2πr² = 2πr(r+h) Homework: pg 692; 7-16