题目

已知∠ACD=90°，MN是过点A的直线，AC=DC，DB⊥MN于点B，如图（1），易证BD+AB= CB，过程如下：过点C作CE⊥CB于点C，与MN交于点E∵∠ACB+∠BCD=90°，∠ACB+∠ACE=90°，∴∠BCD=∠ACE．∵四边形ACDB内角和为360°，∴∠BDC+∠CAB=180°．∵∠EAC+∠CAB=180°，∴BD+AB= CB．∴∠EAC=∠BDC又∵AC=DC，∴△ACE≌△DCB，∴AE=DB，CE=CB，∴△ECB为等腰直角三角形，∴BE= CB．又∵BE=AE+AB，∴BE=BD+AB． （1） 当MN绕A旋转到如图（2）和图（3）两个位置时，BD、AB、CB满足什么样关系式，请写 完形填空 　　In England, people often talk 　　1　　 the 　　2　　 because you can have 　　3　　 seasons in one day．　　4　　 the morning of the day the weather is 　　5　　 just like in spring． 　　An hour 　　6　　, black clouds come, and then it rains hard．The weather gets a 　　7　　 cold．In the late afternoon the sky will clear(晴朗), the sun will begin to shine, it will be 　　8　　 at this time of day．In England, you can also have summer in winter, 　　9　　 have winter in summer．So in winter you can swim sometimes, and in summer sometimes you should 　　10　　 warm clothes． (1) [　　] A． to B． with C． about D． in (2) [　　] A． day B． date C． it D． weather (3) [　　] A． one B． two C． three D． four (4) [　　] A． In B． On C． At D． Of (5) [　　] A． hot B． warm C． cold D． cool (6) [　　] A． later B． late C． latest D． ago (7) [　　] A． lot B． much C． few D． little (8) [　　] A． spring B． summer C． autumn D． winter (9) [　　] A． and B． or C． but D． so (10) [　　] A． wear B． put C． in D． put on