A.對(duì)稱負(fù)載 B.不對(duì)稱負(fù)載 C.平衡負(fù)載 D.不一定對(duì)稱
A.P△=PY B.P△=1/√3PY C.P△=√3PY D.P△=3PY
A.IA+IB+IC=0 B.IA+IB+IC≠0 C.IA+IB+IC=3iA D.IA+IB+IC=(1/3)IA