A.N=-X2sinφ; B.N=êX3sinφ; C.N=-X2cosφ; D.N=êX3sinφ+X2cosφ
A.M=X2y; B.M=X3x; C.M=X1-X2y±X3x; D.M=X1+X2y±X3x
A.只有軸向力; B.只有軸向力和彎矩; C.只有彎矩; D.有軸向力、彎矩和剪力