题目

如图，在△ABC中，∠C=90°，AC=BC，斜边AB=2，O是AB的中点，以O为圆心，线段OC的长为半径画圆心角为90°的扇形OEF，弧EF经过点C，则图中阴影部分的面积为 ． 答案：﹣ ． 【考点】扇形面积的计算． 【分析】连接OC，作OM⊥BC，ON⊥AC，证明△OMG≌△ONH，则S四边形OGCH=S四边形OMCN，求得扇形FOE的面积，则阴影部分的面积即可求得． 【解答】解：连接OC，作OM⊥BC，ON⊥AC． ∵CA=CB，∠ACB=90°，点O为AB的中点， ∴OC=AB=1，四边形OMCN是正方形，OM=． 则扇形FOE的面积是： =． It was not until I received the text message that I knew___a serious disease he had been suffering from,andbegan to worry about___he could pull through  this Christmas. [     ]A.what; whether   B.how ; if    C. that;  that   D .which ; how