已知F1 =20kN, F2 =10kN ,F3 =30kN, F4 =20kN。各X轴和Y轴上的投影为( )
A.
F1x =17.32 kN,F1y=10 kN;F2x =867 kN,F2y=-5 kN;F3x =21.21 kN,F3y=-21.21 kN;F4x =14.14 kN,F4y=-14.14kN
B.
F1x =17.32 kN,F1y=10 kN;F2x =-5 kN,F2y=8.67 kN;F3x =-21.21 kN,F3y=-21.21 kN;F4x =14.14 kN,F4y=-14.14kN
C.
F1x =17.32 kN,F1y=10 kN;F2x =5 kN,F2y=8.67 kN;F3x =21.21 kN,F3y=-21.21 kN;F4x =14.14 kN,F4y=-14.14kN
D.
F1x =10 kN,F1y=17.32kN;F2x =-5 kN,F2y=8.67 kN;F3x =21.21 kN,F3y=-21.21 kN;F4x =14.14 kN,F4y=-14.14kN