在R上可导,且
, 则( )
B .
C .
D . 不能确定

实验次数 | 入射角 | 反射角 |
1 | 20° | 20° |
2 | 45° | 45° |
3 | 60° | 60° |
分析表中数据得出结论是:.进行多次实验的目的是(填A. “防止实验的偶然性” B.“减小实验误差”)
The story was a true one and still moved me deeply. Thirty years ago,I got to know a 1lady named Rose. She had no kids and lived alone. 2I went to visit her,I always took Rose some coffee and food. One day she said she 3 to invite me to have hunch.
We walked from my work place to a little restaurant on David Street 4the way, I began to worry:I knew that she had no money,but if I offered to 5the lunch. I was afraid I would hurt her.
There were many people in the 6and all of them were happy. Rose told me to sit and drink coffee by the window. Then she went to 7in the kitchen. After about 20minutes,she came out and sat with me. She just paid for one meal and we started to 8the delicious food together. She told 9 that the restaurant let people work for a meal if they had no money,or would give them a free meal if they were not able to work. To my surprise,she also explained that the works who were working there were all volunteers. ",10.
I 11remember the beautiful afternoon I shared with Rose. We had a meal together only once,12it was paid by Rose's work. The weather was13and bright,and everyone's smile was warm and bright as well.
I'm still thinking that life cannot be easy to us,but we can still do14for our friends and neighbors. The world will be 15if everybody would like to share happiness with others. It will never be dark if there is a light in everyone's heart.
Who's this man in the picture? Oh, he's a film star. Look, he has a big, long nose.


∥
,
=
+λ
(λ∈R),则λ的值为.
为不重合的两个平面,直线
那么“
”是“
”的( )
尽管(jǐn jìn) 小爪子(zhǎo zhuǎ) 泛着(fá fàn)
骤然(zòu zhòu) 特殊(shū zhū) 呼吁(yù yú)
,再用去它的
,还剩下这根铁丝的( )。
B .
C .
D .
米
B .
C .
D .

①∠AOB+∠BOC=45。;②
=2AB;
③
=10
; ④
= 

,且
,则实数
;集合
的子集的个数为 .
如图1,△ABC和△DEF中,AB=AC,DE=DF,∠A=∠D.

;
的对边(底边)/
的领边(腰)=
,如T(60°)=1.①理解巩固:T(90°)=,T(120°)=,若α是等腰三角形的顶角,则T(α)的取值范围是;
②学以致用:如图2,圆锥的母线长为9,底面直径PQ=8,一只蚂蚁从点P沿着圆锥的侧面爬行到点Q,求蚂蚁爬行的最短路径长(精确到0.1).
(参考数据:T(160°)≈1.97,T(80°)≈1.29,T(40°)≈0.68)