Show that `a.(bxxc)` is equal in magnitude to the volume of the parallelopiped formed on the three vectors a, b and c.

Explanation

Let a parallelopiped be formed on threevectors ` vec(OA) = vec a, vec(OB) = vecb, vec(OC) = vecc`
Now, `vecbxxvecc = bc sin 90^@ hatn = bc hatn`

where `hatn` is the unit vector along `bar(OA)` perpendicular to the plane containing ` vecb " and " vecc`
Nom, ` veca.(vecbxx vecc) a veca. bc hatn = (a)(bc)cos 0^@ = abc`
Which is equal is magnitude to the volume of parallelopiped .