題組內容

4. (10 points) It is known that the definite integral I =66a834bd87391.jpg from 0 to 1 can represent the volume of the solid formed by revolving the region bounded by the curve y = cos x and the lines y = 0, x = 0, x = 66a8350696a72.jpg about the y-axis.

(a) Please give a reason to show that 66a835425f20c.jpg2πxcosx dx . (5 points)