一、选择题（每题4分，共32分）1.如图1，AB是⊙O的切线，B为切点，AO与⊙O交点C，若∠BAO=40°，则∠OCB的度数为·······························（ ）A．40° B．50° C．65° D．75° 图1 图2 图3 图42.如图2是一圆柱形输水管的横截面，阴影部分为有水部分，如果水面AB宽为8 cm，水面最深地的高度为2 cm，则该输水管的半径为（ ）A．3 cm B．4 cm C．5 cm D．6 cm3.圆锥底面圆的半径为3 cm，其侧面展开图是半圆，则圆锥母线长为··························································（ ）A．3 cm B．6 cm C．9 cm D．12 cm4.如图3，边长为a的六角螺帽在桌面上滚动（没有滑动）一，则它的中心O点所经过的路径长为············································（ ）A．6a B．5a C．2aπ D． aπ5.如图4，已知AB是⊙O的直径，AD切⊙O点A，点C是的中点，则下列结论不成立的是····································（ ）A．OC//AE B．EC=BC C．∠DAE=∠ABE D．AC⊥OE6.如图5，动点M，N分别在直线AB与CD上，且 AB//CD，∠BMN与∠MND的平分线相交点P，若以MN为直径作⊙O，则点P与⊙O的位置关系是··················································（ ）A．点P在⊙O外 B．点P在⊙O内 C．点P在⊙O上 D．以上都有可能图5 图67.△ABC中，AB=AC，∠A为锐角，CD为AB边上的高，I为△ACD的内切圆圆心，则∠AIB的度数是········································（ ）A．120° B．125° C．135° D．150°8.如图6，将边长为1 cm的等边三角形ABC沿直线l向右翻动（不滑动），点B从开始到结束，所经过路径的长度为···················（ ）A． π cm B． cm C． π cm D．3 |
