(d) By letting n be large and using a limit involving (sint)/t, show why the limit L of L, as n increases without bound should be 2x. 6. Let r > 0. The equations x = rcos't and y = r sin't parametrizationd (Figure 6.84 in the book). Draw the graph and find the length L of the astroid. (Hint: Square roots are nonnegative!) Review for Chapter 6 1. Let the base of a solid be a 30 - 60 right triangle, with smallest leg of length 2 units on the x axis on the interval [0, 2). The cross sections of the solid perpendicular to that leg are semicircles. Draw a picture of the base, and a cross section, and then find the volume V of the solid. 2. Let f(x) = 4-x2, and let R denote the region bounded above by the graph of f and below by the r axis. Calculate the volume V of the solid generated by revolving R about the line v = -1, and 17