Surface area of revolution worksheet
Each strip of the curve sweeps out a thin band whose area is its circumference times its slant length, 2πr ds. Adding the bands is an integral, and the curves here are chosen so the square root in ds simplifies and the answer comes out exact.
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Sigma Prep · sigmaprep.io/worksheets Name Surface Area of RevolutionDate Period Find the area of each surface. Give exact answers.
Free math worksheets at sigmaprep.io/worksheets© 2026 Sigma Prep |
Sigma Prep · sigmaprep.io/worksheets Name Surface Area of RevolutionAnswer keyVersion 1Date Period Find the area of each surface. Give exact answers.
Free math worksheets at sigmaprep.io/worksheets© 2026 Sigma Prep |
How to do these
Find the area of the surface made by rotating , , about the -axis.
- y' = 1/√x, so 1 + (y')² = (x + 1)/x and ds = √((x + 1)/x) dx.
- The radius is y = 2√x, so 2πy ds = 2π · 2√x · √((x + 1)/x) dx = 4π√(x + 1) dx.
- S = 4π ∫ from 0 to 3 of √(x + 1) dx = 4π · (2/3)[(x + 1)^(3/2)] from 0 to 3 = (8π/3)(8 - 1).
The answer is .
Where students go wrong
Using dx in place of ds. That is the volume formula’s habit: the surface needs the slant length √(1 + (y′)²) dx, and leaving it out gives too small an answer for any curve that is not flat.
Also called area of a surface of revolution, surface area by integration or surface area of a solid of revolution.
What you can put on this worksheet
- About the x-axis
- Find the area of the surface made by rotating , , about the -axis. →
- About the y-axis
- Find the area of the surface made by rotating , , about the -axis. →