KillingForm[elem_{1}, elem_{2}] gives the Killing form between two elements elem_{i} of a linear Lie algebra. 
KillingForm[L][baseElem_{1}, baseElem_{2}] gives the Killing form of Lie algebra L between two base elements baseElem_{i}. 
KillingForm[L, {baseElem_{1}, baseElem_{2}}] gives the Killing form of Lie algebra L between two base elements baseElem_{i}. 
the following commands have the same effect, they give the killing form between the fist element of the chosen base for the Lie algebra
