Exercise 12 Page 872

The given solid is a cone.

To calculate the surface area of a cone, we can use the known formula where r is the radius of the base and l is the slant height of the cone. S=π rl+π r^2 To find the slant height, we can use the Pythagorean Theorem. When doing this, the height l is the hypotenuse. The height and the radius of the cone are the legs. By substituting h with 12 and r with 5, we can solve for l.

By substituting r with 5 and l with 13 into the formula, we can now calculate S.

The surface area of the cone is approximately 282.7ft^2.