—Jerry, ______ eat in the classroom.
—Sorry, I _______.
A:doesn't, don't
B:don't, don't
C:don't, won't
D:not, not
如图,直四棱柱ABCD﹣A1B1C1D1的底面是菱形,侧面是正方形,∠DAB=60°,E是棱CB的延长线上一点,经过点A、C1、E的平面交棱BB1于点F,B1F=2BF.
(1)求证:平面AC1E⊥平面BCC1B1;
(2)求二面角E﹣AC1﹣C的平面角的余弦值.
如图,四边形ABCD内接于半圆O,已知∠ADC=140°,则∠AOC的大小是( )
以“心中有话对你说”为题目,写一篇作文。要求:①可叙述经历,抒发情感。②不少于500字。