题目

The teacher is telling us how water is ________ ice.A. turned up B. turned onC. turned in D. turned into 答案：【答案】D【解析】句意：老师正在告诉我们水是怎样变成冰的。A. turned up调高；B. turned on打开；C. turned in转入；D. turned into变成……。这里是水变成冰。根据题意，故选D。如图，AB为⊙O的直径，C为⊙O上一点，AD和过C点的切线互相垂直，垂足为D，锐角∠DAB的平分线AC交⊙O于点C，作CD⊥AD，垂足为D，直线CD与AB的延长线交于点E．（1）求证：AC平分∠DAB；（2）过点O作线段AC的垂线OE，垂足为E（要求：尺规作图，保留作图痕迹，不写作法）；（3）若CD=4，AC=45，求垂线段OE的长．