F1+S1*cos(L1)-S2*cos(180-L1-L2)-F2*cos(L3)=0
0+S1*sin(L1)+S2*sin(180-L1-L2)-F2*sin(L3)=0
**********************
S1*cos(L1)-S2*cos(180-L1-L2)=F2*cos(L3)-F1
S1*sin(L1)+S2*sin(180-L1-L2)=F2*sin(L3)
**********************
S1=((F2*cos(L3)-F1)*sin(180-L1-L2)+F2*sin(L3)*cos(180-L1-L2))/(cos(L1)*sin(180-L1-L2)+sin(L1)*cos(180-L1-L2))=
=((F2*cos(L3)-F1)*sin(180-L1-L2)+F2*sin(L3)*cos(180-L1-L2))/sin(180-L2)
=((9000*cos(25)-18000)*sin(80))+9000*sin(25)*cos(80))/sin(115)=
-9967,04
S2=(S1*cos(L1)-(F2*cos(L3)-F1))/cos(180-L1-L2)=
=( -9967,04
*cos(35)-(9000*cos(25)-18000))/cos(80)=
9667,292