1. Show that this expression is a total differential of the function u (x, y). Find u (x, y) function
1.18. (X + y) / xydx + (y-x) / y2dy

2. Solve the following tasks:
2.18. Calculate the coordinates of the center of mass of a uniform arc of the first round of the helix x = cost, y = sint, z = 2t.

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