Answer:
289 cm²
Step-by-step explanation:
The net for the surface area of a cone is a circular sector representing the lateral area, together with a circle representing the area of the base. The arc length of the sector is equal to the circumference of the base.
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<h3>base area</h3>
The area of the circular base is given by the area formula for a circle:
A = πr²
For the given radius, the area is ...
A = (3.14)(4 cm)² = 50.24 cm²
<h3>lateral area</h3>
The circumference of the circular base is ...
C = 2πr = 2(3.14)(4 cm) = 25.12 cm . . . . also the arc length of the sector
The area of the sector is ...
A = 1/2hs . . . . where h is the radius of the sector, and s is its arc length
A = (1/2)(19 cm)(25.12 cm) = 238.64 cm²
<h3>total surface area</h3>
The total surface area is the sum of the base area and the lateral area:
SA = 50.24 cm² +238.64 cm² = 288.88 cm² ≈ 289 cm²
The surface area of the cone is about 289 cm².