(2) (4 marks) Solve the following: (a) If C is the line segment connecting the point (x1, y1) to the point (12, y2), show that x dy - y dx = 142 - 291. (b) If the vertices of a polygon, in counterclockwise order, are (x1, y1), (x2, y2), . .. (n, Un), show that the area of the polygon is A = (2192 - X2y1) + (293 - 342) + ... (n-1Un -Knyn-1) + (Xnyl - X1yn) ]. (c) Find the area of the pentagon with vertices (0, 0), (2, 1), (1, 3) (0, 2), and (-1, 1)