在△ABC中,∠BAC=90°,AB=AC.点D从点B出发沿射线BC移动,以AD为边在AB的右侧作△ADE,且∠DAE=90°,AD=AE.连接CE. (1)如图1,若点D在BC边上,则∠BCE= º; (2)如图2,若点D在BC的延长线上运动. ①∠BCE的度数是否发生变化?请说明理由; ②若BC=3,CD=6,则△ADE的面积为 . 答案:解:(1)90…………………2分 (2)①不发生变化. ∵AB=AC,∠BAC=90° ∴∠ABC=∠ACB=45°…………………3分 ∵∠BAC=∠DAE=90° ∴∠BAC+∠DAC=∠DAE+∠DAC ∴∠BAD=∠CAE…………………4分 在△ACE和△ABD中 AC=AB ∠CAE=∠BAD AE=AD ∴△ACE≌△ABD…………………5分 ∴∠ACE=∠ABD=45° ∴∠BCE=∠BCA+∠ACE=45°
No sooner had he arrived than he to complain about the terrible
weather.
[ ]
A.
began
B.
would begin
C.
had begun
D.
begins