A.hf1=hf2B.hf1〉hf2C.hf1〈hf2D.無法確定
A.重合B.不重合C.在某瞬時(shí)于某空間點(diǎn)相切D.正交
A.159.3kN/m2B.43.3kN/m2C.-58kN/m2D.-43.3kN/m2