k =( KT − ST− FD )−( KF − SD )
vector{[red]A[/red]B} +vector{B[red]C[/red]}= vector{[red]AC[/red]}
vector{AB} =-vector{BA}
Раскрываем скобки:
vector{k} =vector{KT} -vector{ST}− vector{FD} −vector{ KF} + vector{SD}
vector{k} =vector{[red]K[/red]T} +vector{T[red]S[/red]}− vector{FD} −vector{ KF} + vector{SD} =
=vector{[red]K[/red]S} + vector{S[red]D[/red]} -vector{FD} -vector{ FK}=
==vector{[red]K[/red]D}+vector{D[red]F[/red]} -vector{ KF}=vector{KF} -vector{ KF}=vector{0}