2022年初中數(shù)學(xué)旋轉(zhuǎn)全等

28分將一塊三角板的直角頂點放在正方形的對交置邊角線重合如圖甲，將塊三角板繞直角點順時方向旋轉(zhuǎn)旋轉(zhuǎn)角小于90°）如圖．試eq\o\ac(△,斷)ODEeq\o\ac(△,和)是等，并證你的論．

D

D若正形的對角線長，試三板正方形重部的積．

O

O

甲

F乙（第2題）25題分分）圖（不全等等腰直三形OAB和放在一起并且有共的直角點．將圖（a）中eq\o\ac(△,的)OAB繞點O時轉(zhuǎn)角圖（）出旋轉(zhuǎn)后eq\o\ac(△,的)（留作圖痕跡不寫法不證明．在圖（）中，發(fā)線，BD的量關(guān)系直線，BD交

度．（3）圖（a）eq\o\ac(△,的)OAB點O順時針旋轉(zhuǎn)一個銳角，得到圖（時（）的兩個結(jié)論是否成立？作出判斷并說明由若eq\o\ac(△,．)繞點O繼續(xù)旋轉(zhuǎn)更大的角時，論仍成嗎？作出判，不說理由．

Ｏ

圖（）

圖（）

圖（c）17．如，正方形ABCD中點在邊上，在邊BA的上.）DCF順時針方向旋轉(zhuǎn)后恰好eq\o\ac(△,與)合則旋轉(zhuǎn)中心點度；（2）（）條件下，AE,求邊形BFDE積E

D

FB在中，ACB為，點為射線BC上一動點，連結(jié)，將段AD繞點

時針轉(zhuǎn)到，結(jié)EC。（）果C，當點在段BC上（點重合,請斷線段之間的位置關(guān)系數(shù)量關(guān)系（直寫出結(jié)論當點在段BC的線上時，請你在中形，并中的結(jié)否仍然成立，并明你的斷。A

AEB

D

B

圖

圖（點線段BC上運動DFAD交段于點F，

，求線段CF的值。E

D圖

F答案28）證明全等，略⑵，解）如圖（a（B字位置互換扣分，無扣分連結(jié)扣分，完為）······························································································3分（2）；

（空分）······················································分（3）成立．如圖（b）Ｏ

F圖（a）∵COD90AOD

圖（b）即：DOB

（或由轉(zhuǎn)

DOB

）··································7分∵OA

eq\o\ac(△,)COAeq\o\ac(△,)DOB

·····································分ACBD

···························································································9分延長COD于E，于F下的法多）eq\o\ac(△,)COA

eq\o\ac(△,)DOB

，ACOODB

················································10分∵

∴90

AC

···············分旋更大角時，論仍然成立．································································分17．）；.2分）與△合，eq\o\ac(△,