Page 61 - Calculus for the Clueless, Calc II
P. 61
Exaple 17—
Find the surface area of a sphere of radius a.
A sphere is a semicircle rotated about the x-axis (or y-axis): x = a cos t; dx/dt = -a sin t; y = a sin t; dy/dt = a cos
t.
The math under the square root sign simplifies to a . So we get...
2
2
Again we haven't been lied to all these years. The surface area of a sphere really is 4πa .
