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Surface Area of a Cone = πr2 + πrs
To find the surface area of a cone, we need to find the area of the circular base and the area of the curved section. This one involves a new measurement, s, which is the length of the slanted part.
If you take apart the cone, you get two surfaces, the circular base, and the curved sides. The area of the base is just πr2, and the area of the curved section is πrs. So, the total surface area of a cone is πr2 +πrs.
Look Out: surface area is only two-dimensional and is expressed as units squared, not units cubed. This is because we are only dealing with the flat surfaces, not the inside space.