Question

Shown below is a cuboid. Find `vec(BA).vec(BC)`.

Shown below is a cuboid. Find `vec(BA) * vec(BC)`.

Answer 1

Taking the coordinate axes as shown in the diagram, the coordinates are A(2, 0, 0), B(0, 4, 3) and C(1, 4, 0).

`vec(BA) = vecA - vecB`

= (2 − 0, 0 − 4, 0 − 3)

= (2, −4, −3)

= `2 hati - 4hatj - 3hatk`

`vec(BC) = vecC - vecB`

= (1 − 0, 4 − 4, 0 − 3)

= (1, 0, −3)

= `hati - 3hatk`

`vec(BA) * vec(BC)`

= (2) (1) + (−4) (0) + (−3) (−3)

= 2 + 0 + 9

= 11