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12.4 S urface Areas of Cylinders

By Bailee and Kayla. 12.4 S urface Areas of Cylinders. Objectives. Find lateral areas of cylinders Find surface areas of cylinders. Lateral Areas of Cylinders.

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12.4 S urface Areas of Cylinders

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  1. By Bailee and Kayla 12.4 Surface Areas of Cylinders

  2. Objectives • Find lateral areas of cylinders • Find surface areas of cylinders

  3. Lateral Areas of Cylinders • The axis of the cylinder is the segment with the endpoints that are centers of the circular bases. If the axis is also the altitude, then the cylinder is called a right cylinder. Otherwise, the cylinder is an oblique cylinder.

  4. Tidbit of Knowledge • The net of a cylinder is composed of two congruent circles and a rectangle. • The area of this rectangle is the lateral area. • The length of the rectangle is the same as the circumference of the base, 2 r2 • So, the lateral area of a right cylinder is 2 rh base base

  5. Example • Find the lateral area of a right circular cylinder whose base has a radius of 4 inches and whose height is 6 inches. • 4 6

  6. Using the formula L=2 rh, we get… 2 x 3.14 x 6 x 4 equals 150.72 units 2 • 4 6

  7. Surface Area • If a right cylinder has a surface area of T units 2, a height of h units, and the bases have radii of r units, then T= 2 rh + 2 r 2. • So basically, it’s the lateral area of the rectangle plus the area of the two bases (circles). Get it? 

  8. Example • The diameter of the base of a cylinder is 12 cm and the height is 8 cm. Find the surface area of the solid cylinder. 12cm 8cm

  9. Using T= 2 rh + 2 r 2 Plug it in: 2 x 3.14 x 6 x 8 + 2 x 3.14 x 6 2 Equals 301.44 + 226.08 So your answer should be. . . 527.5 cm 2

  10. Another Example • Find the missing radius

  11. How to do it

  12. Assignment Page 657-658 # 9-20, 24, 25, 28 Have a wonderful day!  ♥

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