She thought it was worthwhile for her to teach in the small village to make a ______ to the life of the children there.
A:difference
B:sense
C:study
D:discovery
如图1,平行四边形纸片ABCD的面积为120,AD=20,AB=18,沿两条对角线将四边形ABCD剪成甲、乙、丙、丁四个三角形纸片,将甲、丙拼成如图2所示的轴对称图形戊,则图形戊的两条对角线长度之和为( )
已知函数f1(x)=lg1-x2x2-2-2;f2(x)=(x﹣1)•x+1x-1;f3(x)=loga(x+x2+1),(a>0,a≠1);f4(x)=x•(12x-1+12),(x≠0),下面关于这四个函数奇偶性的判断正确的是( )
***于1935年2月在《忆秦峨.娄山关》中写道:“雄关漫道真如铁,而今迈步从头越。”“从头越”是指( )