(sector area) / (large circle area) = (arc length) / (large circle circumference) so: The formula can be obtained from proportions, as the ratio of the areas of the shapes is the same as the ratio of the arc length to the circumference: The area of a sector - which is our lateral surface of a cone - is given by the formula:Ī(lateral) = (s × (arc length)) / 2 = (s × 2 × π × r) / 2 = π × r × s The arc length of the sector is equal to 2 × π × r. It's a circular sector, which is the part of a circle with radius s ( s is the cone's slant height).įor the circle with radius s, the circumference is equal to 2 × π × s. Let's have a look at this step-by-step derivation: The base is again the area of a circle A(base) = π × r², but the lateral surface area origins maybe not so obvious: A = A(lateral) + A(base), as we have only one base, in contrast to a cylinder.We may split the surface area of a cone into two parts:
LATERAL AREA RECTANGULAR PRISM FORMULA HOW TO
Surface area of a pyramid: A = l × √(l² + 4 × h²) + l², where l is a side length of the square base and h is a height of a pyramid.īut where do those formulas come from? How to find the surface area of the basic 3D shapes? Keep reading, and you'll find out! Surface area of a triangular prism: A = 0.5 × √((a + b + c) × (-a + b + c) × (a - b + c) × (a + b - c)) + h × (a + b + c), where a, b and c are the lengths of three sides of the triangular prism base and h is a height (length) of the prism. Surface area of a rectangular prism (box): A = 2(ab + bc + ac), where a, b and c are the lengths of three sides of the cuboid. Surface area of a cone: A = πr² + πr√(r² + h²), where r is the radius and h is the height of the cone. Surface area of a cylinder: A = 2πr² + 2πrh, where r is the radius and h is the height of the cylinder.
Surface area of a cube: A = 6a², where a is the side length. Surface area of a sphere: A = 4πr², where r stands for the radius of the sphere. The formula depends on the type of solid. Our surface area calculator can find the surface area of seven different solids.
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