Solution
= Solution
Using $\varepsilon_{ijk}\varepsilon_{klm}=\delta_{il}\delta_{jm}-\delta_{im}\delta_{jl}$,
$[\nabla\times(F\times G)]_i=\partial_j(F_iG_j)-\partial_j(F_jG_i)$; expanding the <derivatives> gives the stated four terms.
= Solution
Using $\varepsilon_{ijk}\varepsilon_{klm}=\delta_{il}\delta_{jm}-\delta_{im}\delta_{jl}$,
$[\nabla\times(F\times G)]_i=\partial_j(F_iG_j)-\partial_j(F_jG_i)$; expanding the <derivatives> gives the stated four terms.