Question

Find the value of p, for which the vectors `veca = 3hati + 2hatj + 9hatk` and `vecb = hati + phatj + 3hatk` are perpendicular to each other.

Answer 1

`veca * vecb = 0`

`(3hati + 2hatj + 9hatk) * (hati + phatj + 3hatk) = 0`

(3 × 1) + (2 × p) + (9 × 3) = 0

3 + 2p + 27 = 0

2p + 30 = 0

2p = –30

p = –15