Use vectors to decide whether the triangle with vertices

Question

P(3, −3, 0), Q(4, 0, −2), and R(8, −2, −3)
is right-angled.

I feel like this uses the cross product but I'm not sure how.

Answer 1

PQ^2=1+9+4=14
PR^2=25+1+9=35
QR^2=16+4+1=21