A:144(1−x)2=100
B:144(1+x)2=100
C:100(1+x)2=144
D:100(1−x)2=144
一把大遮阳伞伞面撑开时可近似地看成是圆锥形,如图,它的母线长是2.5米,底面半径为2米,则伞面的面积是( )
—What a lovely card! Where did you buy it?—I made it by _______.
____的作用是保持鱼体侧立,对鱼体平衡起着关键作用。