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The area A of the region S that lies under the graph of the continuous function is the limit of the sum of the areas of approximation rectangles. A = lim R = lim [f(x, )Ax + f(x2)Ax +. . . + f(x, )4x] n - co Use this definition to find an expression for the area under the graph of f as a limit. Do not evaluate the limit. f(x) = 9x cos(9x), 0