If `vecb and vecc` are two non-collinear such that `veca ||(vecbxxvecc)`. Then prove that `(vecaxxvecb).(vecaxxvecc)` is equal to `|veca|^(2)(vecb.vecc)` `

Explanation

`veca||(vecbxxvecc)`
`veca=lambda(vecbxxvecc)and veca=vecabotvecband vecabotvecc`
`Now, (vecaxxvecb).(vecaxxvecc)=|{:(veca.a,veca.vecc),(vecb.veca,vecb.vecc):}|`
`=|{:(veca.veca,0),(0,vecb.vecc):}|=|veca|^(2)(vecb.vecc)`