X Y X M Y Y Y M M M X Y P q q M P=q*L P=q*L/2 L 0.5L 0.5L L 2L/3 L/3 a a 2a P A B P A B Y X Y A A B A=0 A+YB-P=0 A=0 => YB.L-P.L/2=0 => YB=P/2 A=0; YA=YB=P/2 a Y2 Y1 b A MA1 quay 2 Y1.b-Y2.a=0 q q a b q q a b X Y Y C B C A B C A B C AB BC QAB=q*a/2 q a b Y Y B C A B C 2a/3 a/3 b/2 b/2 QBC=q*b X=0 C=0 Y=0 ta YB+YC-(q.a/2+q.b)=0 MC=0 suy ra: QBC.b.2+QAB.(b+a/3)-YB.b=0 => q.b.b/2+q.a.(b+a/3)-YB.b=0 => YB XC=0 YB YC 4060 20 2 2 2 4 2 4060 20 2 4 2 Y Y B A XA-20.2=0XA=40 A X 20.2.1+40 -YB.4-60=0 YB=5 YA-YB=0YA=5 C A B D C E P=20 q=10 q=10 F B E P=20 q=10 F X Y B B Y E 10.4.2+20.4-YE.2=0 suy ra YE=80 B, YB XB=0 YB+10.4+20-YE=0 YB=20 A B D q=10 thanh CD RCD Y X XB=0 YB=20 RCD. CD A A B B YB XB Y'B X'B XB=X'B YB=Y'B XB X'BB Y'B B P RCD.Cos60.4+YB.6-10.6.3=0 suy ra RCD=30 X C . 2 4060 20 2 4 2 Y Y B A XA-20.2=0XA=40 A X 20.2 .1+ 40 -YB. 4-6 0=0 YB=5 YA-YB=0YA=5 C A B D C E P=20 q =10 q =10 F B E P=20 q =10 F X Y B B Y E . YA=YB=P/2 a Y2 Y1 b A MA 1 quay 2 Y1.b-Y2.a=0 q q a. b/2 QBC=q*b X=0 C=0 Y=0 ta YB+YC-(q.a/2+q.b)=0 MC=0 suy ra: QBC.b.2+QAB.(b+a/3)-YB.b=0 => q.b.b/2+q.a.(b+a/3)-YB.b=0 => YB XC=0 YB YC 4060 20 2 2 2