题目

—_______            —Nothing serious, but a bit tired.            —Better have a rest now, dear.              A. Is that all?              B. Is there anything else?              C. What’s this?              D. What’s the matter with you? 答案：D已知：如图，扇形OAB和扇形OA′B′的圆心角相同，设AA′=BB′=d．AB=l1，A′B′=l2．求证：图中阴影部分的面积S=12(l1+l2)d．