题目

如图，直角三角形的直角顶点在坐标原点，∠OAB=30°，若点A在反比例函数y=（x＞0）的图象上，则经过点B的反比例函数解析式为（ ）A. y=﹣ B. y=﹣ C. y=﹣ D. y= 答案：【答案】C【解析】直接利用相似三角形的判定与性质得出，进而得出S△AOD=3，即可得出答案．过点B作BC⊥x轴于点C，过点A作AD⊥x轴于点D，∵∠BOA=90°，∴∠BOC+∠AOD=90°，∵∠AOD+∠OAD=90°，∴∠BOC=∠OAD，又∵∠BCO=∠ADO=90°，∴△BCO∽△ODA，∵=tan30°=，∴，∵×AD×DO=xy=3，∴S△BCO=×BC×CO=S△AOD=1，∵经过点BSome equipment as well as a number of maps and books _____to Zhouqu since the mud-rock flow occurred. A. has been offered                       B. have been offered C. are offered                       D. is being offered