A:where does she live
B:where she lives in
C:where she lives
计算: 12 +( 12 )﹣1﹣(3﹣π)0﹣|1﹣4cos30°|
一物体做匀速直线运动,4s内通过了4m的距离,那么它在前2s内的运动速度是( )