CLP-3 Multivariable Calculus (Feldman, Rechnitzer, and Yeager)
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This textbook covers multivariable Calculus. There are chapters on vectors and geometry in 2 and 3 dimensions, partial derivatives, and multivariable integrals.
Thumbnail: A diagram depicting a worked triple integral example. The questions is "Find the volume of the region bounded above by the sphere x2+y2+z2=a2 and below by the cone z2sin2(a)=(x2+y2)cos2(a) where a is in the interval [0,π] (Public Domain; Inductiveload via Wikipedia).