3.画弯矩图 X2 XI M=-FAXI B 0<x1<a a x1=0M=0 M M=, -Mo-Mox a≤x2≤l R x =a m=-M x=l M=03.画弯矩图 0 A 1 1 M M F x x l = − = − 1 0   x a 0 0 2 0 2 A M M M F x M x l = − = − 2 a x l   1x = 0 M = 0 1 x a = 0 a M Ml = − 2 x a = 0 b M Ml = 2 x l = M = 0 A B C M 0 a b L x 1 x 2