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lecture notes 13

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.Definition. Let S be a parameterized surface or a graph, then thesurface ∫∫ area ∫∫of √S is given by1 dS = 1 + z 2 x + z 2 y dxdy, orS ∫∫ D= ∥r u × r v ∥ dudv..D.Example.Find the area of the part of the surface 2z = x 2 that liesdirectly above the triangle in the xy-plane with vertices at. A(0, 0), B(1, 0) and C(1, 1).Solution. The surface is a graph z(x, y) = x 2 /2 defined on the regionD = { (x, y) | 0 ≤ x ≤ 1, 0 ≤ y ≤ x }, then z x = x and z y = 0. Thesurface ∫∫ √area is1 + z 2 x + x 2 y dxdy∆ABC. . . . . .

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