如图, AB=AC ,BD=BC,若∠A=50°,则∠ABD=度数是( )
A:15°
B:20°
C:25°
D:30°
First-class players of football must have excellent ball control, but it is not just _____ they do with their feet _____ counts.
某物体做初速度为零的匀加速直线运动,加速度为2m/s2.求: