Glencoe Math: Course 3, Volume 2
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Glencoe Math: Course 3, Volume 2 View details
5. Surface Area of Cones
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Exercise 21 Page 637

The lateral area of a right cone is half the product of the circumference of the base and the slant height.

452.4in.^2

Practice makes perfect
We want to find the lateral area of the cone with a radius of 9 millimeters and a slant height of 16 millimeters. To do so, we must know that the lateral area of a right cone is half the product of the circumference of the base and the slant height. L.A.=1/2* 2π r* l ⇔ L.A.=π rl In this formula, r is the radius and l is the slant height of the cone. With this information we are able to calculate the lateral area of the cone. To do so, we will substitute r= 9 and l= 16 into the formula for the lateral area. Let's do it!
L.A.=π rl
L.A.=π ( 9)( 16)
L.A.=π (144)
L.A.=144π
L.A.=452.389342...
L.A.≈ 452.4
The lateral area of the given cone, to the nearest tenth, is 452.4 square inches.